A112887 Semiprime(n) - composite(n).

0, 0, 1, 1, 4, 3, 7, 7, 9, 8, 13, 13, 13, 14, 14, 20, 22, 23, 25, 25, 25, 28, 30, 33, 36, 38, 42, 43, 42, 42, 45, 45, 45, 45, 55, 59, 61, 63, 63, 64, 64, 63, 67, 70, 70, 76, 76, 75, 76, 76, 83, 84, 84, 85, 89, 91, 97, 97, 101, 101, 102, 108, 114, 114, 113, 114, 114, 116, 119

Offset

1,5

Comments

The first occurrence where the sequence has k similar terms: 4, 0, 13, 45, 857, 523807, 119, ...

Links

Table of n, a(n) for n=1..69.

Mathematica

Select[ Range@225, Plus @@ Last /@ FactorInteger@# == 2 &] - Select[ Range[2, 102], !PrimeQ[ # ] &]

Crossrefs

Cf. A002808, A001358.

Sequence in context: A131413 A249189 A168200 * A351684 A305035 A352832

Adjacent sequences: A112884 A112885 A112886 * A112888 A112889 A112890

Keyword

nonn

Author

Robert G. Wilson v, Dec 31 2005

Extensions

Definition corrected by Juri-Stepan Gerasimov, May 17 2010

Status

approved