A049996 a(n) is the index k such that F(k)=d(n), where d=A049874 (difference sequence of ordered products of Fibonacci numbers).

1, 1, 1, 3, 1, 3, 3, 4, 3, 1, 5, 4, 3, 6, 5, 1, 3, 7, 6, 3, 4, 8, 7, 3, 1, 5, 9, 8, 4, 3, 6, 10, 9, 5, 1, 3, 7, 11, 10, 6, 3, 4, 8, 12, 11, 7, 3, 1, 5, 9, 13, 12, 8, 4, 3, 6, 10, 14, 13, 9, 5, 1, 3, 7, 11, 15, 14, 10, 6, 3, 4, 8, 12, 16, 15, 11, 7, 3, 1, 5, 9, 13, 17

Offset

1,4

Links

Michel Marcus, Table of n, a(n) for n = 1..1010

Mathematica

Block[{nn = 123, s, t}, s = Differences@ Take[#, nn] &@ Union@ Flatten[Table[Fibonacci[i]*Fibonacci[j], {i, 0, nn}, {j, i + 1, nn}]]; t = Fibonacci@ Range@ nn; Array[First@ FirstPosition[t, s[[#]] ] &, Length@ s]] (* Michael De Vlieger, May 27 2019 *)

Prog

(PARI) ifib(n) = if (n==1, 1, log(n*sqrt(5) + 1/2)\log((1+sqrt(5))/2));
lista(nn) = {my(out = List([0])); for (i=0, nn, for (j=i+1, nn, listput(out, fibonacci(i)*fibonacci(j)); ); ); my(v = Vec(vecsort(select(x->(x < fibonacci(nn+1)), out), , 8))); my(w = vector(#v-1, k, v[k+1] - v[k])); vector(#w, k, ifib(w[k])); } \\ Michel Marcus, May 27 2019

Crossrefs

Cf. A049862, A049874.

Sequence in context: A136297 A243339 A244965 * A344793 A143908 A349814

Adjacent sequences: A049993 A049994 A049995 * A049997 A049998 A049999

Keyword

nonn

Author

Clark Kimberling

Extensions

More terms from Michel Marcus, May 27 2019

Status

approved