

A023395


Only Fermat number divisible by A023394(n) is 2^2^a(n) + 1.


1



0, 1, 2, 3, 5, 4, 12, 6, 11, 11, 9, 5, 18, 12, 10, 12, 23, 16, 15, 10, 19, 12, 19, 13, 36, 21, 38, 32, 25, 17, 39, 6, 26, 27, 30, 30, 8, 12, 15, 29, 38, 7, 25, 27, 36, 42, 25, 13, 13, 55
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OFFSET

1,3


LINKS

Table of n, a(n) for n=1..50.
Wilfrid Keller, Prime factors k.2^n + 1 of Fermat numbers F_m


PROG

(PARI) forprime(p=3, , r=znorder(Mod(2, p)); hammingweight(r)==1&&print1(logint(r, 2)1, ", ")) \\ Jeppe Stig Nielsen, Mar 04 2018


CROSSREFS

Cf. A000215, A023394.
Sequence in context: A193971 A258861 A171038 * A316655 A318848 A193798
Adjacent sequences: A023392 A023393 A023394 * A023396 A023397 A023398


KEYWORD

nonn,more


AUTHOR

David W. Wilson


EXTENSIONS

a(25)a(41) computed using data from Wilfrid Keller by T. D. Noe, Feb 01 2009
Three more terms by T. D. Noe, Feb 03 2009
Six more terms from Wilfrid Keller by T. D. Noe, Jan 14 2013


STATUS

approved



