A131516 a(n)=1 if n is an odd prime number, otherwise, a(n)=n.

0, 1, 2, 1, 4, 1, 6, 1, 8, 9, 10, 1, 12, 1, 14, 15, 16, 1, 18, 1, 20, 21, 22, 1, 24, 25, 26, 27, 28, 1, 30, 1, 32, 33, 34, 35, 36, 1, 38, 39, 40, 1, 42, 1, 44, 45, 46, 1, 48, 49, 50, 51, 52, 1, 54, 55, 56, 57, 58, 1, 60, 1, 62, 63, 64, 65, 66, 1, 68

Offset: 0

Author

Mohammad K. Azarian, Aug 14 2007

Keywords

• nonn
• easy

Programs

Mathematica

Table[If[OddQ[n]&&PrimeQ[n],1,n],{n,0,68}] (* James C. McMahon, Feb 27 2025 *)

PARI

a(n) = if ((n%2) && isprime(n), 1, n); \\ Michel Marcus, Nov 13 2013

Extensions

Offset corrected by Ivan Panchenko, Nov 13 2013