A128978 a(1) = 1, a(2) = 1 and a(n) = number of terms among (a(1),a(2),...a(n-1)) which divide (a(n-1)+a(n-2)).

1, 2, 1, 2, 2, 5, 2, 2, 7, 2, 2, 9, 2, 2, 11, 2, 2, 13, 3, 13, 13, 16, 2, 16, 16, 17, 4, 4, 16, 17, 4, 4, 18, 15, 4, 2, 16, 18, 17, 4, 4, 22, 18, 23, 2, 3, 3, 19, 18, 2, 25, 6, 2, 25, 6, 2, 26, 27, 2, 2, 28, 28, 31, 2, 6, 29, 4, 6, 23, 3, 26, 3, 3, 32, 4, 46, 25, 2, 10, 42, 37, 2, 11, 5, 38, 2

Offset

1,2

Comments

a(n) = 2 for n's: 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 23, 36, 45, 50, 53, 56, 59, 60, 64, 78, 82, 86, ....

First occurrence of k: 1, 2, 19, 27, 6, 52, 9, 186, 12, 79, 15, 255, 18, 107, 34, 22, 26, 33, 48, 134, 205, 42, 44, 381, 51, ....

Links

Table of n, a(n) for n=1..86.

Mathematica

f[s_List] := Block[{}, Append[s, Count[ Mod[ s[[ -1]] + s[[ -2]], s], 0]]]; Nest[f, {1, 2}, 85] (* Robert G. Wilson v *)

Crossrefs

Cf. A128923.

Sequence in context: A258783 A079318 A050315 * A325110 A357888 A145862

Adjacent sequences: A128975 A128976 A128977 * A128979 A128980 A128981

Keyword

nonn

Author

Robert G. Wilson v and Leroy Quet, Apr 29 2007

Status

approved