A127432 a(0)=1. a(n) = number of earlier terms a(k), 0<=k<=n-1, such that (k+n) is divisible by a(k).

1, 1, 2, 2, 3, 4, 3, 4, 4, 5, 3, 7, 5, 5, 5, 5, 6, 8, 5, 4, 8, 8, 5, 9, 6, 6, 8, 8, 7, 9, 7, 9, 10, 9, 4, 10, 9, 8, 12, 7, 7, 11, 9, 9, 9, 12, 9, 13, 11, 7, 9, 12, 10, 12, 9, 9, 12, 12, 13, 13, 8, 10, 13, 14, 6, 12, 12, 12, 17, 10, 11, 14, 12, 12, 9, 14, 11, 16, 13, 12, 14, 13, 9, 16, 16, 12, 13

Offset

0,3

Links

Rémy Sigrist, Table of n, a(n) for n = 0..10000

Rémy Sigrist, C program for A127432

Example

(0+9) is a multiple of a(0)=1; (1+9) is a multiple of a(1)=1; (3+9) is a multiple of a(3)=2; (6+9) is a multiple of a(6)=3 and (7+9) is a multiple of a(7)=4. These five cases are the only cases where (k+n) is divisible by a(k), for 0<=k<=8. So a(9) = 5.

Mathematica

f[l_List] := Block[{n = Length[l]}, Append[l, Count[Table[Mod[k + n - 1, l[[k]]], {k, n}], 0]]]; Nest[f, {1}, 87] (* Ray Chandler, Jan 22 2007 *)

Prog

(C) See Links section.

Crossrefs

Cf. A127431, A127434.

Sequence in context: A056796 A061295 A081742 * A199408 A285325 A135529

Adjacent sequences: A127429 A127430 A127431 * A127433 A127434 A127435

Keyword

nonn,look

Author

Leroy Quet, Jan 14 2007

Extensions

Extended by Ray Chandler, Jan 22 2007

Status

approved