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A128001 Numbers n such that (n-1)*2^n+1 is prime. 2
2, 3, 7, 27, 51, 55, 81, 1471, 1483, 8668, 10885, 20803, 32605, 36391, 57004, 61627, 88651, 89731 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

Select[Range[200], PrimeQ[(# - 1)*2^# + 1] &]  (* G. C. Greubel, May 08 2018 *)

PROG

(PARI) is(n)=ispseudoprime((n-1)<<n+1) \\ Charles R Greathouse IV, Jun 06 2017

CROSSREFS

Cf. A029544, A002064.

Sequence in context: A092983 A089708 A107881 * A264829 A156142 A052877

Adjacent sequences:  A127998 A127999 A128000 * A128002 A128003 A128004

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, Jan 25 2008

EXTENSIONS

a(8)-a(14) from Jason Earls, Jan 29 2008

a(15)-a(18) from Charles R Greathouse IV, Oct 09 2011

STATUS

approved

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Last modified June 26 10:12 EDT 2019. Contains 324375 sequences. (Running on oeis4.)