A268657 Numbers k such that 3*2^k + 1 is a prime factor of a generalized Fermat number 3^(2^m) + 1 for some m.

6, 12, 18, 30, 36, 41, 66, 189, 201, 209, 276, 408, 438, 534, 2208, 3168, 3189, 3912, 34350, 42294, 44685, 48150, 54792, 55182, 59973, 80190, 157169, 213321, 303093, 382449, 709968, 801978, 916773, 1832496, 2145353, 2291610, 2478785, 5082306, 7033641, 10829346

Offset

1,1

References

Wilfrid Keller, private communication, 2008.

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..41

Anders Björn and Hans Riesel, Factors of generalized Fermat numbers, Math. Comp. 67 (1998), no. 221, pp. 441-446.

Anders Björn and Hans Riesel, Table errata to “Factors of generalized Fermat numbers”, Math. Comp. 74 (2005), no. 252, p. 2099.

Anders Björn and Hans Riesel, Table errata 2 to "Factors of generalized Fermat numbers", Math. Comp. 80 (2011), pp. 1865-1866.

C. K. Caldwell, Top Twenty page, Generalized Fermat Divisors (base=3)

OEIS Wiki, Generalized Fermat numbers

Prog

(PARI) for(k=1, +oo, p=3*2^k+1; if(ispseudoprime(p), t=znorder(Mod(3, p)); bitand(t, t-1)==0&&print1(k, ", "))) \\ Jeppe Stig Nielsen, Oct 30 2020

Crossrefs

Cf. A059919, A268658, A204620, A268659, A268660, A268661, A268662, A268663, A226366, A268664. Subsequence of A002253.

Sequence in context: A057826 A334543 A330853 * A232742 A268928 A162864

Adjacent sequences: A268654 A268655 A268656 * A268658 A268659 A268660

Keyword

nonn

Author

Arkadiusz Wesolowski, Feb 10 2016

Status

approved