A176100 Even numbers that are not semiprimes, or, twice the nonprimes.

0, 2, 8, 12, 16, 18, 20, 24, 28, 30, 32, 36, 40, 42, 44, 48, 50, 52, 54, 56, 60, 64, 66, 68, 70, 72, 76, 78, 80, 84, 88, 90, 92, 96, 98, 100, 102, 104, 108, 110, 112, 114, 116, 120, 124, 126, 128, 130, 132, 136, 138, 140, 144, 148, 150, 152, 154, 156, 160, 162, 164

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 08 2010, Apr 11 2010

Keywords

• nonn
• easy

Crossrefs

Cf. A001358, A005843, A100484, A141468.

Programs

Mathematica

2 Prepend[Select[Range@ 82, ! PrimeQ@ # &], 0] (* Michael De Vlieger, Feb 20 2017 *)

PARI

isok(n) = !(n%2) && !isprime(n/2); \\ Michel Marcus, Feb 20 2017

Formula

a(n)= 2*A141468(n).

A005843 \ A100484.

a(n) = A139270(n-1). [R. J. Mathar, May 03 2010]

Extensions

Entries checked by R. J. Mathar, Apr 16 2010