

A127431


a(1)=1. a(n) = number of earlier terms a(k), 1<=k<=n1, such that (k+n) is divisible by a(k).


3



1, 1, 2, 2, 3, 3, 4, 3, 5, 5, 4, 4, 7, 3, 6, 8, 5, 5, 6, 5, 8, 8, 5, 6, 10, 5, 8, 8, 9, 7, 7, 8, 9, 9, 8, 9, 12, 5, 8, 12, 8, 9, 10, 7, 13, 9, 13, 11, 10, 7, 9, 12, 11, 9, 11, 10, 18, 8, 8, 10, 16, 10, 9, 12, 11, 11, 14, 13, 13, 12, 10, 15, 12, 10, 15, 11, 15, 12, 11, 13, 14, 12, 12, 13, 18, 9, 14
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OFFSET

1,3


LINKS



EXAMPLE

(1+11) is a multiple of a(1)=1; (2+11) is a multiple of a(2)=1; (3+11) is a multiple of a(3)=2; and (9+11) is a multiple of a(9)=5. These four cases are the only cases where (k+n) is divisible by a(k), for 1<=k<=10. So a(11) = 4.


MATHEMATICA

f[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[Table[Mod[k + n, l[[k]]], {k, n  1}], 0]]]; Nest[f, {1}, 86] (* Ray Chandler, Jan 22 2007 *)


PROG

(C) See Links section.


CROSSREFS



KEYWORD



AUTHOR



EXTENSIONS



STATUS

approved



