OFFSET
0,1
COMMENTS
EXAMPLE
a(0) = 2 because
1) 2^1 + (6*0+3) = 5 and (6*0+3)*2^1 - 1 = 5 for k = 1 < (6*0+3);
2) 2^2 + (6*0+3) = 7 and (6*0+3)*2^2 - 1 = 11 for k = 2 < (6*0+3).
a(1) = 3 because
1) 2^1 + (6*1+3) = 11 and (6*1+3)*2^1 - 1 = 17 for k = 1 < (6*1+3);
2) 2^3 + (6*1+3) = 17 and (6*1+3)*2^3 - 1 = 71 for k = 3 < (6*1+3);
3) 2^7 + (6*1+3) = 137 and (6*1+3)*2^7 - 1 = 1151 for k = 7 < (6*1+3).
a(2) = 5 because
1) 2^1 + (6*2+3) = 17 and (6*2+3)*2^1 - 1 = 29 for k = 1 < (6*2+3);
2) 2^2 + (6*2+3) = 19 and (6*2+3)*2^2 - 1 = 59 for k = 2 < (6*2+3);
3) 2^4 + (6*2+3) = 31 and (6*2+3)*2^4 - 1 = 239 for k = 4 < (6*2+3);
4) 2^5 + (6*2+3) = 37 and (6*2+3)*2^5 - 1 = 479 for k = 5 < (6*2+3);
5) 2^10 + (6*2+3) = 1039 and (6*2+3)*2^10 - 1 = 15359 for k = 10 < (3*2+3).
PROG
(PARI) for(n=0, 100, m=0; for(k=0, 6*n+2, if(isprime(2^k+6*n+3) && isprime((6*n+3)*2^k-1), m++)); print1(m, ", ")) \\ Colin Barker, Mar 25 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Lopatin and Juri-Stepan Gerasimov, Mar 20 2014
EXTENSIONS
Offset changed to 0 by Colin Barker, Mar 25 2014
STATUS
approved