A065090 Natural numbers which are not odd primes: composites plus 1 and 2.

1, 2, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Formula

A151763(a(n)) = 0.

Prog

(PARI) { n=0; for (m=1, 10^9, if (!isprime(m) || m==2, write("b065090.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Oct 06 2009
(Haskell)
import Data.List (elemIndices)
a065090 n = a065090_list !! (n-1)
a065090_list = map (+ 1) $ elemIndices 0 a151763_list
-- Reinhard Zumkeller, Oct 06 2011
(Python)
from sympy import composite
def A065090(n): return composite(n-2) if n>2 else n # Chai Wah Wu, Jul 13 2024

Crossrefs

Cf. A002808, A006005.

Complement of A065091.

Sequence in context: A189466 A085492 A338924 * A371167 A324560 A355822

Adjacent sequences: A065087 A065088 A065089 * A065091 A065092 A065093

Keyword

nonn,easy

Author

Labos Elemer, Nov 12 2001

Status

approved