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A123885
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a(1)=1. a(n) = a(n-1) + (number of earlier terms {i.e., terms a(1) through a(n-1)} that divide n).
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2
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1, 2, 3, 5, 7, 10, 12, 14, 16, 20, 21, 25, 26, 30, 33, 36, 37, 40, 41, 46, 50, 52, 53, 57, 60, 63, 65, 69, 70, 76, 77, 80, 83, 85, 88, 93, 95, 97, 99, 105, 107, 113, 114, 116, 119, 122, 123, 128, 130, 136, 138, 142, 144, 147, 149, 153, 156, 158, 159, 168, 169, 171, 176
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..63.
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EXAMPLE
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Among terms a(1) through a(5) there are three terms that divide 6: a(1)=1, a(2)=2 and a(3)=3. So a(6) = a(5) + 3 = 10.
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MAPLE
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A123885 := proc(maxn) local a, nexta, n, i; a := [1]; for n from 2 to maxn do nexta := op(n-1, a); for i from 1 to n-1 do if n mod op(i, a) = 0 then nexta := nexta +1; fi; od; a := [op(a), nexta]; od; RETURN(a); end: maxn := 100 : alist := A123885(maxn) : for i from 1 to maxn do printf("%d, ", op(i, alist)); end : # R. J. Mathar, Oct 21 2006
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MATHEMATICA
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f[l_List] := Append[l, Last[l] + Length[Select[l, Mod[Length[l] + 1, # ] == 0 &]]]; Nest[f, {1}, 63] (* Ray Chandler, Oct 19 2006 *)
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CROSSREFS
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Cf. A123886.
Sequence in context: A346592 A254860 A144726 * A010062 A119565 A119592
Adjacent sequences: A123882 A123883 A123884 * A123886 A123887 A123888
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KEYWORD
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easy,nonn
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AUTHOR
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Leroy Quet, Oct 17 2006
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EXTENSIONS
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Extended by Ray Chandler, Oct 19 2006
More terms from R. J. Mathar, Oct 21 2006
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STATUS
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approved
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