A138301 - OEIS

%I #3 Mar 31 2012 13:22:05

%S 1,2,4,11,37,145,673,3748,22875

%N Number of integers k < 10^n such that k*(k+1)-1 and k*(k+3)-1 are both first of twin primes.

%e 3*4-1=11 11 and 13 twin primes, 3*6-1=17 17 and 19 twin primes a(1)=1

%e 15*16-1=239 239 and 241 twin primes, 15*18-1=269 269 and 271 twin primes a(2)=2

%Y Cf. A138303.

%K nonn

%O 1,2

%A _Pierre CAMI_, Mar 14 2008