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1,5

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

Table of n, a(n) for n=1..105.

Cf. A072742, A072743, A071538.

Sequence in context: A209899 A111898 A279041 * A179528 A105390 A013941

Adjacent sequences: A072743 A072744 A072745 * A072747 A072748 A072749

nonn

Reinhard Zumkeller, Jul 08 2002

approved