A212956 - OEIS

%I #10 Jun 01 2012 12:34:37

%S 1,13,91,209,213,217,8,283,82,3150,105,3729,3548,1267,5218,3459,571,

%T 1911,12088,858,4606,3171,5305,6890,5024,19149,14766,16640,15333,

%U 39382,8692,49314,53630,123600,4120,57993,47136,20530,115743,30022,31457,76736,25842

%N Least k such that k*30^n-1 , k*30^n+1, and 2*k*30^n-1 are prime; that is, twin primes and a Sophie Germain prime.

%H Pierre CAMI, <a href="/A212956/b212956.txt">Table of n, a(n) for n = 1..125</a>

%e 1*30^1-1 = 29, 1*30^1+1 = 31, 2*1*30^1-1 = 59. Because 29, 31, and 59 are prime, a(1) = 1.

%t Table[k = 1; While[! PrimeQ[k*30^n + 1] || ! PrimeQ[k*30^n - 1] || ! PrimeQ[2 k*30^n - 1], k++]; k, {n, 50}] (* _T. D. Noe_, Jun 01 2012 *)

%o PFGW64 and SCRIPTIFY from Primeform Group

%o command: pfgw64 -f in.txt

%o in.txt file :

%o SCRIPT

%o DIM nn,0

%o DIM kk,0

%o DIMS tt

%o OPENFILEOUT myfil,b(n).txt

%o LABEL loopn

%o SET nn,nn+1

%o IF nn>125 THEN END

%o SET kk,0

%o LABEL loopk

%o SET kk,kk+1

%o SETS tt,%d,%d\,;nn;kk

%o PRP kk*30^nn-1,tt

%o IF ISPRP THEN GOTO a

%o IF ISPRIME THEN GOTO a

%o GOTO loopk

%o LABEL a

%o PRP kk*30^nn+1,tt

%o IF ISPRP THEN GOTO b

%o IF ISPRIME THEN GOTO b

%o GOTO loopk

%o LABEL b

%o PRP 2*kk*30^nn-1,tt

%o IF ISPRP THEN GOTO c

%o IF ISPRIME THEN GOTO c

%o GOTO loopk

%o LABEL c

%o WRITE myfil,tt

%o GOTO loopn

%Y Cf. A212955.

%K nonn

%O 1,2

%A _Pierre CAMI_, Jun 01 2012