A071701 Number of twin prime pairs <= n of form (4*k+1,4*k+3), k>0.

0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4

Offset: 1

Author

Reinhard Zumkeller, Jun 04 2002

Keywords

• nonn

Comments

As for A071538 the convention is followed that a twin prime pair is <= n if its smaller member is <= n.

Examples

			a(30)=3, since (29,31) is included along with (5,7) and (17,19).
		

Crossrefs

a(n) = A071538(n) - A071702(n), cf. A071695, A071696.