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A049495 a(n) and a(n)+4^k are primes at least for k=1,2,3,4,5. 4
7, 37, 163, 9157, 9277, 15667, 53593, 56893, 111577, 135193, 137383, 142543, 305407, 467527, 470647, 476023, 480043, 527377, 607093, 671353, 761377, 817147, 885943, 891643, 904663, 1080073, 1116637, 1140847, 1172803, 1233523 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..1000

EXAMPLE

7, 7+4=11, 7+16=23, 7+64=71, 7+256=263, 7+1024=1031 are all primes; the smallest such a sextuple is {7,11,23,71,263,1031}.

MATHEMATICA

Select[Prime@ Range[10^5], Function[p, AllTrue[Range@ 5, PrimeQ[p + 4^#] &]]] (* Michael De Vlieger, Aug 09 2017 *)

PROG

(PARI) isok(n) = isprime(n) && isprime(n+4) && isprime(n+16) && isprime(n+64) && isprime(n+256) && isprime(n+1024); \\ Michel Marcus, Dec 22 2013

CROSSREFS

Cf. A023200, A049492-A049494, A049496-A049500.

Sequence in context: A247308 A175284 A049494 * A169789 A169726 A305781

Adjacent sequences:  A049492 A049493 A049494 * A049496 A049497 A049498

KEYWORD

nonn

AUTHOR

Labos Elemer

STATUS

approved

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Last modified August 12 21:10 EDT 2020. Contains 336440 sequences. (Running on oeis4.)