A095306 - OEIS

A095306

Numbers n such that r(k) * 2^n + 1 is prime, where r() = A002275 the repunits and k is the number of decimal digits of 2^n.

1, 2, 5, 12, 19, 107, 117, 159, 217, 517, 868, 1412, 1636, 4051, 5965, 9128

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OFFSET

1,2

COMMENTS

a(1) through a(16) have been proved to be prime with WinPFGW. a(16) has 5495 digits. No more terms up to 11700.

Results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019

LINKS

EXAMPLE

a(5)=19 because 111111 * 2^19 + 1 = 58254163969, a prime.

CROSSREFS

KEYWORD

more,nonn,base

AUTHOR

Jason Earls, Jul 13 2004

STATUS

approved