login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Let q = 1 + a(n)*2^n. Then q is least prime such that A098006(pi(q)) = 2^(n-1). 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 10 01:38 EDT 2020. Contains 336361 sequences. (Running on oeis4.)