

A128978


a(1) = 1, a(2) = 1 and a(n) = number of terms among (a(1),a(2),...a(n1)) which divide (a(n1)+a(n2)).


0



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
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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 A145862 A058701
Adjacent sequences: A128975 A128976 A128977 * A128979 A128980 A128981


KEYWORD

nonn


AUTHOR

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


STATUS

approved



