1,4

a(n) = A000720(A001358(n+1)) - A000720(A001358(n));

a(A088701(n))=n and a(k)<>n for 1<=k < A088701(n).

a(n) = 0 for almost all n. The average order of a(n) is 1/log log n. - Charles R Greathouse IV, Apr 29 2012

T. D. Noe, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Prime Counting Function

Eric Weisstein's World of Mathematics, Semiprime

a(34)=3, as there are three primes between A001358(34)=19*5=95

and A001358(34+1)=53*2=106: 97, 101 and 103.

Cf. A103668 (semiprimes between primes).

Cf. A214520 (primes that are the only prime between consecutive semiprimes).

Sequence in context: A039974 A039973 A035171 * A287121 A035446 A126211

Adjacent sequences: A088697 A088698 A088699 * A088701 A088702 A088703

nonn

Reinhard Zumkeller, Oct 08 2003

approved