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A269544 Numbers n such that 7*8^n + 1 is prime. 2
2, 40, 58, 60, 130, 144, 752, 7462, 18162, 69028, 187272, 268178, 270410, 497284, 713304, 722600, 1005254 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) is even because 7*8^(2*k+1) + 1 is divisible by 3.

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a(n) = A032353(n)/3 where this is an integer.

MATHEMATICA

Select[Range[0, 200000, 2], PrimeQ[7*8^# + 1] &]

PROG

(PARI) is(n)=ispseudoprime(7*8^n+1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A056799, A245241, A268061.

Sequence in context: A213909 A073418 A275547 * A281761 A012477 A003760

Adjacent sequences:  A269541 A269542 A269543 * A269545 A269546 A269547

KEYWORD

nonn,hard,more

AUTHOR

Robert Price, Feb 29 2016

STATUS

approved

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Last modified November 22 18:55 EST 2019. Contains 329410 sequences. (Running on oeis4.)