A177745 -id:A177745 - cp's OEIS frontend

A177086 Semiprimes k that divide Fibonacci(k-1).

1891, 4181, 8149, 13201, 15251, 17711, 40501, 51841, 64079, 64681, 67861, 68251, 78409, 88601, 88831, 90061, 96049, 97921, 115231, 118441, 145351, 146611, 153781, 191351, 197209, 218791, 219781, 254321, 272611, 302101, 303101

Offset: 1

Jonathan Vos Post, Dec 09 2010

This is the semiprime (A001358) analog of A045468. Now A045468 has a very simple characterization: it consists of the primes ending in 1 or 9. Can one say anything about the present sequence?

			46368/23 = 2016 = 2^5 * 3^2 * 7 so (24-1) | Fibonacci(24) but 24 is not semiprime, so is not in the sequence.
a(1) = 1891 = 31 * 61 is not in the sequence because 1891 divides Fibonacci(1891-1) = Fibonacci(1890).
a(21) = 146611 = 271 * 541 because 146611 | Fibonacci(146610).

Chai Wah Wu, Table of n, a(n) for n = 1..837

Cf. A000040, A000045, A001358, A069106, A045468, A003631, A064739, A081264 (Fibonacci pseudoprimes).

Cf. A177745 (semiprimes k that divide Fibonacci(k+1)).

Select[Range[310000],PrimeOmega[#]==2 && Divisible[Fibonacci[#-1],#]&] (* Harvey P. Dale, May 02 2016 *)

{k: k is in A001358 and k|A000045(k-1)} = A069106 INTERSECTION A001358.

cp's OEIS Frontend

A177086 Semiprimes k that divide Fibonacci(k-1).

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