A082462 Let chi(k) = 1 if prime(k+1) - prime(k) = 2, = 0 otherwise; sequence gives a(n) = sum_{k <= n} chi(k).

0, 1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 10, 10, 10, 10, 10, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 17, 17, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21

Offset: 1

Author

Artemario Tadeu Medeiros da Silva (artemario(AT)uol.com.br), Apr 26 2003

Keywords

• nonn

Examples

			n p D a(n) (p=prime(n), D = prime(n+1)-prime(n))
1 2 1 0
2 3 2 1
3 5 2 2
4 7 4 2
5 11 2 3
6 13 4 3
		

Crossrefs

Cf. A000040, A001223.

Formula

a(n)=A071538(A000040(n)). [From R. J. Mathar, Oct 06 2008]