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A252734 Smallest odd prime Q such that Q^2*2^prime(n)-1 is a prime number starting with n=2. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 25 01:31 EDT 2021. Contains 346273 sequences. (Running on oeis4.)