A138301 Number of integers k < 10^n such that k*(k+1)-1 and k*(k+3)-1 are both first of twin primes.

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

Offset

1,2

Links

Table of n, a(n) for n=1..9.

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

Cf. A138303.

Sequence in context: A174107 A253927 A281481 * A367495 A173939 A328433

Adjacent sequences: A138298 A138299 A138300 * A138302 A138303 A138304

Keyword

nonn

Author

Pierre CAMI, Mar 14 2008

Status

approved