A112325 Number of even semiprimes <= semiprime(n).

1, 2, 2, 3, 4, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 9, 9, 9, 10, 11, 11, 11, 12, 12, 13, 13, 14, 14, 14, 14, 15, 15, 16, 16, 16, 17, 17, 17, 18, 18, 18, 18, 19, 19, 20, 20, 20, 21, 21, 22, 22, 22, 23, 23, 23, 24, 24, 24, 24, 25, 25, 26, 26, 26, 27, 27, 27, 28, 28, 28, 29, 29, 29, 30

Offset

1,2

Links

Table of n, a(n) for n=1..76.

Mathematica

spQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; sp = Select[Range@300, spQ[ # ] &]; f[n_] := Length[Select[Take[sp, n], EvenQ[ # ] &]]; Array[f, 76] (* Robert G. Wilson v *)

Crossrefs

Sequence in context: A060018 A089576 A076642 * A135304 A249037 A029111

Adjacent sequences: A112322 A112323 A112324 * A112326 A112327 A112328

Keyword

nonn

Author

Giovanni Teofilatto, Dec 01 2005

Extensions

More terms from Stefan Steinerberger and Robert G. Wilson v, Dec 02 2005

Status

approved