A252734 Smallest odd prime Q such that Q^2*2^prime(n)-1 is a prime number starting with n=2.

3, 7, 3, 5, 3, 5, 83, 5, 7, 43, 11, 23, 3, 71, 47, 97, 109, 13, 19, 17, 53, 83, 97, 53, 43, 97, 5, 3, 43, 17, 19, 13, 307, 103, 293, 13, 11, 457, 113, 317, 67, 47, 311, 127, 281, 3, 97, 13, 127, 1223, 61, 307, 29

Offset

2,1

Links

Pierre CAMI, Table of n, a(n) for n = 2..1800

Example

3^2*2^3-1=71 prime so a(2)=3.
7^2*2^5-1=1567 prime so a(3)=7.

Mathematica

Table[k=3; While[Not[PrimeQ[k^2*2^Prime[n]-1]], k=NextPrime[k]]; k, {n, 2, 100}] (* Vaclav Kotesovec, Dec 21 2014 *)

Prog

(PFGW & SCRIPT)
SCRIPT
DIM n, 1
DIM q
OPENFILEOUT myf, a(n).txt
LABEL loop1
SET n, n+1
SET q, 1
LABEL loop2
SET q, q+1
PRP p(q)^2*2^p(n)-1
IF ISPRP THEN GOTO a
GOTO loop2
LABEL a
WRITE myf, q
GOTO loop1

Crossrefs

Cf. A252733.

Sequence in context: A021968 A132821 A247217 * A101636 A193534 A096247

Adjacent sequences: A252731 A252732 A252733 * A252735 A252736 A252737

Keyword

nonn

Author

Pierre CAMI, Dec 21 2014

Status

approved