

A134855


Least odd prime p such that 1 + p*2^n is also prime.


3



3, 3, 5, 7, 3, 3, 5, 3, 23, 13, 29, 3, 5, 7, 5, 37, 53, 3, 11, 7, 11, 37, 71, 73, 5, 7, 17, 13, 23, 3, 239, 43, 113, 163, 59, 3, 89, 349, 5, 97, 3, 73, 11, 67, 101, 19, 101, 61, 23, 7, 17, 7, 233, 127, 5, 541, 29, 103, 71, 31, 53, 109, 179, 163, 71, 3, 929, 31, 23, 193, 101, 127
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OFFSET

1,1


COMMENTS

Let q = 1 + a(n)*2^n. Then q is least prime such that A098006(pi(q)) = 2^(n1). See A134854 for the values of q.
a(n) = prime(k) for some k < 5*n for n <= 10000 .  Pierre CAMI, Jul 20 2014


LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10000 (First 1000 terms from T. D. Noe)


MATHEMATICA

Table[Select[Prime[Range[2, 10000]], PrimeQ[1+2^k # ]&, 1][[1]], {k, 100}]


PROG

(PARI) a(n) = p=3; t=2^n; while(!isprime(1+p*t), p=nextprime(p+1)); p \\ Colin Barker, Jul 22 2014


CROSSREFS

Cf. A098006, A134854.
Sequence in context: A092035 A164914 A247479 * A335045 A110246 A070543
Adjacent sequences: A134852 A134853 A134854 * A134856 A134857 A134858


KEYWORD

nonn


AUTHOR

T. D. Noe, Nov 13 2007


STATUS

approved



