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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 11 22:31 EST 2019. Contains 329046 sequences. (Running on oeis4.)