A113637 In the sequence of positive integers subtract 1 from each nonprime number.

0, 2, 3, 3, 5, 5, 7, 7, 8, 9, 11, 11, 13, 13, 14, 15, 17, 17, 19, 19, 20, 21, 23, 23, 24, 25, 26, 27, 29, 29, 31, 31, 32, 33, 34, 35, 37, 37, 38, 39, 41, 41, 43, 43, 44, 45, 47, 47, 48, 49, 50, 51, 53, 53, 54, 55, 56, 57, 59, 59, 61, 61, 62, 63, 64, 65, 67, 67, 68, 69, 71, 71, 73

Offset: 1

Author

Cino Hilliard, Jan 15 2006

Keywords

• easy
• nonn

Crossrefs

Cf. A113636, A113638.

Programs

Mathematica

Table[If[PrimeQ[n],n,n-1],{n,73}] (* James C. McMahon, Jul 07 2024 *)

PARI

a(n) = if (isprime(n), n, n-1); \\ Michel Marcus, Jul 08 2024