OFFSET
1,2
EXAMPLE
3*4-1=11 11 and 13 twin primes, 3*6-1=17 17 and 19 twin primes a(1)=1
15*16-1=239 239 and 241 twin primes, 15*18-1=269 269 and 271 twin primes a(2)=2
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Mar 14 2008
STATUS
approved