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A280873
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Numbers whose binary expansion does not begin 10 and do not contain 2 adjacent 0's; Ahnentafel numbers of X-chromosome inheritance of a male.
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5
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0, 1, 3, 6, 7, 13, 14, 15, 26, 27, 29, 30, 31, 53, 54, 55, 58, 59, 61, 62, 63, 106, 107, 109, 110, 111, 117, 118, 119, 122, 123, 125, 126, 127, 213, 214, 215, 218, 219, 221, 222, 223, 234, 235, 237, 238, 239, 245, 246, 247, 250, 251, 253, 254, 255
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refs;
listen;
history;
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internal format)
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OFFSET
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0,3
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COMMENTS
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The number of ancestors at generation n from whom a living individual may have received an X chromosome allele is Fn, the n-th term of the Fibonacci Sequence.
From Antti Karttunen, Oct 11 2017: (Start)
The starting offset is zero (with a(0) = 0) for the same reason that we have A003714(0) = 0. Indeed, b(n) = A054429(A003714(n)) for n >= 0 yields the terms of this sequence, but in different order.
A163511(a(n)) for n >= 0 gives a permutation of squarefree numbers (A005117). See also A277006.
(End)
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LINKS
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Antti Karttunen, Table of n, a(n) for n = 0..10946
David Eppstein, Self-recursive generators (Python recipe)
L. A. D. Hutchison, N. M. Myres and S. R. Woodward, Growing the Family Tree: The Power of DNA in Reconstructing Family Relationships, Proceedings of the First Symposium on Bioinformatics and Biotechnology (BIOT-04, Colorado Springs), pp. 42-49, Sept. 2004.
Index entries for sequences related to binary expansion of n
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MAPLE
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gen[0]:= {0, 1, 3}:
gen[1]:= {6, 7}:
for n from 2 to 10 do
gen[n]:= map(t -> 2*t+1, gen[n-1]) union
map(t -> 2*t, select(type, gen[n-1], odd))
od:
sort(convert(`union`(seq(gen[i], i=0..10)), list)); # Robert Israel, Oct 11 2017
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MATHEMATICA
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male = {1, 3}; generations = 8;
Do[x = male[[i - 1]]; If[EvenQ[x],
male = Append[ male, 2*x + 1] ,
male = Flatten[Append[male, {2*x, 2*x + 1}]]]
, {i, 3, Fibonacci[generations + 1]}]; male
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PROG
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(PARI)
isA003754(n) = { n=bitor(n, n>>1)+1; n>>=valuation(n, 2); (n==1); }; \\ After Charles R Greathouse IV's Feb 06 2017 code.
isA004760(n) = (n<2 || (binary(n)[2])); \\ This function also from Charles R Greathouse IV, Sep 23 2012
isA280873(n) = (isA003754(n) && isA004760(n));
n=0; k=0; while(k <= 10946, if(isA280873(n), write("b280873.txt", k, " ", n); k=k+1); n=n+1; ); \\ Antti Karttunen, Oct 11 2017
(Python)
def A280873():
yield 1
for x in A280873():
if ((x & 1) and (x > 1)):
yield 2*x
yield 2*x+1
def take(n, g):
'''Returns a list composed of the next n elements returned by generator g.'''
z = []
if 0 == n: return(z)
for x in g:
z.append(x)
if n > 1: n = n-1
else: return(z)
take(120, A280873())
# Antti Karttunen, Oct 11 2017, after the given Mathematica-code (by Floris Strijbos) and a similar generator-example for A003714 by David Eppstein (cf. "Self-recursive generators" link).
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CROSSREFS
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Cf. A003714, A054429.
Intersection of A003754 and A004760.
Positions where A163511 obtains squarefree (A005117) values.
Cf. also A293437 (a subsequence).
Sequence in context: A333000 A175048 A294231 * A293437 A359756 A350943
Adjacent sequences: A280870 A280871 A280872 * A280874 A280875 A280876
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KEYWORD
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nonn,base
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AUTHOR
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Floris Strijbos, Jan 09 2017
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EXTENSIONS
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a(0) = 0 prepended and more descriptive alternative name added by Antti Karttunen, Oct 11 2017
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STATUS
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approved
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