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1,2

The case n=1 is special and defined conventionally.

a(n) = A034386(n)/A034386(1+floor((n+1)/2)).

Notice that the interval is semiopen; a prime p is included in the product if (n+1)<2p<=2n.

Stanislav Sykora, Table of n, a(n) for n = 1..1000

a(13) = product of all primes in (7,13] = 11*13 = 143.

(PARI:){p2(n) = result=1; forprime(p=1+floor((n+1)\2), n, result=result*p); }

Cf. A212791, A034386.

Sequence in context: A134408 A051032 A106530 * A050976 A053447 A185026

Adjacent sequences: A212789 A212790 A212791 * A212793 A212794 A212795

nonn

Stanislav Sykora, May 27 2012

approved