A119249 Indices of Fibonacci numbers in A081952.

4, 7, 10, 17, 22, 31, 41, 47, 49, 71, 71, 98, 119, 161, 169, 191, 191, 239, 239, 239, 338, 338, 338, 431, 431, 449, 529, 599, 649, 649, 769, 769, 769, 769, 769, 769, 1009, 1009, 1009, 1409, 1441, 1441, 1441, 1441, 1729, 1889, 1889, 1889, 1889, 2159, 2209, 2209, 2209, 2591, 2642, 2642

Offset: 1

Author

Ryan Propper, Jul 22 2006

Keywords

• nonn

Examples

			A081952(4) = 1597 and 1597 is the 17th Fibonacci number, so a(4) = 17.
		

Crossrefs

Cf. A000045, A000071, A081952, A086435.

Programs

Mathematica

f[n_, m_, 0] := n == 1; f[n_, m_, d_] := (b = False; l = Select[Divisors[n], #>=m&]; For[i = 1, i <= Length[l], i++, k = l[[i]]; If[f[n / k, k + 1, d - 1], b = True; Break[]]]; b); Do[x = 3; While[ !f[Fibonacci[x] - 1, 2, y], x++ ]; Print[x], {y, 1, 50}]

Formula

A081952(n) = F(a(n)), where F(k) is the k-th Fibonacci number.

a(n) = the smallest k>3 such that A086435(A000045(k)-1)>=n. - Max Alekseyev, Apr 23 2010

Extensions

a(24)-a(26) from Max Alekseyev, Apr 23 2010

a(27)-a(56) from Amiram Eldar, Jun 24 2023