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A056977
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Number of blocks of {0, 1, 1} in binary expansion of n.
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10
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1
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OFFSET
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1,91
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LINKS
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Gheorghe Coserea, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Digit Block
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FORMULA
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a(2n) = a(n), a(2n+1) = a(n) + [n>1 and n congruent to 1 mod 4]. - Ralf Stephan, Aug 22 2003
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MATHEMATICA
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a[n_, bits_] := (idn = IntegerDigits[n, 2]; ln = Length[idn]; lb = Length[bits]; For[cnt = 0; k = 1, k <= ln - lb + 1, k++, If[idn[[k ;; k + lb - 1]] == bits, cnt++]]; cnt); Table[ a[n, {0, 1, 1}], {n, 1, 102} ] (* Jean-François Alcover, Oct 23 2012 *)
Table[SequenceCount[IntegerDigits[n, 2], {0, 1, 1}], {n, 120}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 03 2019 *)
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PROG
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(PARI)
a(n) = {
if (n < 11, return(0));
my(k = logint(n, 2) - 1);
hammingweight(bitnegimply(bitand(n>>1, n), n>>2)) - bittest(n, k)
};
vector(102, i, a(i)) \\ Gheorghe Coserea, Sep 17 2015
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CROSSREFS
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Cf. A014082, A056974, A056975, A056976, A056977, A056978, A056979, A056980.
Sequence in context: A277007 A160380 A122433 * A309144 A085425 A355685
Adjacent sequences: A056974 A056975 A056976 * A056978 A056979 A056980
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KEYWORD
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nonn,easy
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AUTHOR
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Eric W. Weisstein
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STATUS
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approved
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