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A224490 Smallest k such that k*2*p(n)^2-1=q is prime and k*2*q^2-1 is also prime. 9
1, 1, 25, 9, 21, 3, 1, 16, 25, 136, 10, 33, 90, 250, 10, 55, 1, 9, 36, 75, 1, 4, 33, 406, 103, 15, 121, 4, 244, 78, 28, 19, 49, 105, 45, 34, 10, 46, 33, 4, 111, 15, 9, 36, 118, 66, 10, 13, 31, 76, 66, 36, 55, 15, 4, 48, 6, 66, 13, 34, 54, 64, 153, 1, 60, 48 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10000

EXAMPLE

1*2*2^2-1=7 prime q 1*2*7^2-1=97 also prime so a(1)=1.

MATHEMATICA

a[n_] := For[k = 1, True, k++, p = Prime[n]; If[PrimeQ[q = k*2*p^2 - 1] && PrimeQ[k*2*q^2 - 1], Return[k]]]; Table[a[n], {n, 1, 66}] (* Jean-Fran├žois Alcover, Apr 12 2013 *)

PROG

SCRIPT

DIM k

DIM i, 0

DIM q

DIMS t

OPENFILEOUT myf, a(n).txt

LABEL a

SET i, i+1

IF i>20000 THEN END

SET k, 0

LABEL b

SET k, k+1

SETS t, %d, %d, %d\,; k; i; p(i)

SET q, k*2*p(i)^2-1

PRP q, t

IF ISPRP THEN GOTO c

GOTO b

LABEL c

SET q, k*2*q^2-1

PRP q, t

IF ISPRP THEN WRITE myf, t

IF ISPRP THEN GOTO a

GOTO b

CROSSREFS

Cf. A224489, A224491, A224492.

Sequence in context: A065910 A096521 A215539 * A226224 A181763 A171638

Adjacent sequences:  A224487 A224488 A224489 * A224491 A224492 A224493

KEYWORD

nonn

AUTHOR

Pierre CAMI, Apr 08 2013

EXTENSIONS

Typo in name fixed by Zak Seidov, Apr 11 2013

STATUS

approved

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)