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 A227576 Numbers n such that F(3*n)/(2*F(n)) is prime, where F(k) is the k-th Fibonacci number. 1
 5, 7, 11, 13, 17, 31, 37, 41, 67, 107, 151, 257, 349, 457, 787, 911, 1289, 1627, 3271, 8233, 13163, 14551, 31517, 55579 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. Conjecture: this sequence is infinite. LINKS EXAMPLE For n = 5 we have F(3*5)/(2*F(5)) = F(15)/(2*5) = 610/10 = 61 is prime. MATHEMATICA Select[Range[1000], PrimeQ[Fibonacci[3*#]/Fibonacci[#]/2] &] (* Vaclav Kotesovec, Jul 18 2013 *) PROG (PARI) forprime(p=5, 1e4, if(ispseudoprime(t=fibonacci(3*p)/fibonacci(p) /2), print1(p", "))) \\ Charles R Greathouse IV, Jul 16 2013 (PFGW) ABC2 F(3*\$a)/2/F(\$a) a: primes from 5 to 25000 // Charles R Greathouse IV, Jul 16 2013 CROSSREFS Cf. A001605, A000045, A227627. Sequence in context: A109416 A132170 A106309 * A114262 A255229 A230217 Adjacent sequences: A227573 A227574 A227575 * A227577 A227578 A227579 KEYWORD nonn,more AUTHOR Thomas Ordowski, Jul 16 2013 EXTENSIONS a(6)-a(22) from Charles R Greathouse IV, Jul 16 2013 a(23) from Vaclav Kotesovec, Jul 18 2013 a(24) from Charles R Greathouse IV, Jul 18 2013 STATUS approved

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Last modified November 27 14:41 EST 2022. Contains 358405 sequences. (Running on oeis4.)