OFFSET
0,4
EXAMPLE
a(2) = 1 because
1) 2^10 - (6*2+3) = 1009 and (6*2+3)*2^10 + 1 = 15361 for k = 10 < (6*2+3).
a(3) = 3 because
1) 2^5 - (6*3+3) = 11 and (6*3+3)*2^5 + 1 = 673 for k = 5 < (6*3+3);
2) 2^7 - (6*3+3) = 107 and (6*3+3)*2^7 + 1 = 2689 for k = 7 < (6*3+3);
3) 2^9 - (6*3+3) = 491 and (6*3+3)*2^9 + 1 = 10753 for k = 9 < (6*3+3).
PROG
(PARI) for(n=0, 120, 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 26 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Lopatin and Juri-Stepan Gerasimov, Mar 25 2014
EXTENSIONS
a(24), a(76) and a(86) corrected by Colin Barker, Mar 26 2014
STATUS
approved