cp's OEIS Frontend

A205780 Least positive integer k such that n divides C(k)-C(j) for some j in [1,k-1], where C=A007598 (squared Fibonacci numbers).

%I A205780 #6 Dec 04 2016 19:46:26
%S A205780 2,3,2,3,3,4,4,3,5,5,5,4,5,6,5,4,7,6,7,5,4,7,7,4,9,7,7,6,7,5,8,6,6,7,
%T A205780 6,6,8,9,5,6,10,6,10,7,10,10,8,6,11,9,9,7,9,7,5,6,9,9,12,5,13,13,5,8,
%U A205780 8,10,19,7,12,13,11,6,11,19,9,9,8,8,23,6,10,12,22,6,10,10,8,7,9
%N A205780 Least positive integer k such that n divides C(k)-C(j) for some j in [1,k-1], where C=A007598 (squared Fibonacci numbers).
%C A205780 For a guide to related sequences, see A204892.
%e A205780 1 divides C(2)-C(1) -> k=2, j=1
%e A205780 2 divides C(3)-C(1) -> k=3, j=1
%e A205780 3 divides C(2)-C(1) -> k=2, j=1
%e A205780 4 divides C(3)-C(1) -> k=3, j=1
%e A205780 5 divides C(3)-C(2) -> k=3, j=2
%t A205780 s = Table[(Fibonacci[n + 1])^2, {n, 1, 120}];
%t A205780 lk = Table[
%t A205780   NestWhile[# + 1 &, 1,
%t A205780    Min[Table[Mod[s[[#]] - s[[j]], z], {j, 1, # - 1}]] =!= 0 &], {z, 1,
%t A205780     Length[s]}]
%t A205780 Table[NestWhile[# + 1 &, 1,
%t A205780   Mod[s[[lk[[j]]]] - s[[#]], j] =!= 0 &], {j, 1, Length[lk]}]
%t A205780 (* _Peter J. C. Moses_, Jan 27 2012 *)
%Y A205780 Cf. A204892, A007598.
%K A205780 nonn
%O A205780 1,1
%A A205780 _Clark Kimberling_, Feb 01 2012