A259175 a(n) = 1 if n prime, otherwise prime(n).

2, 1, 1, 7, 1, 13, 1, 19, 23, 29, 1, 37, 1, 43, 47, 53, 1, 61, 1, 71, 73, 79, 1, 89, 97, 101, 103, 107, 1, 113, 1, 131, 137, 139, 149, 151, 1, 163, 167, 173, 1, 181, 1, 193, 197, 199, 1, 223, 227, 229, 233, 239, 1, 251, 257, 263, 269, 271, 1, 281, 1, 293, 307, 311

Offset: 1

Author

Vincenzo Librandi, Jun 20 2015

Keywords

• nonn
• easy

Comments

The subsequence of prime terms is A007821. - Michel Marcus, Jun 20 2015

Examples

			a(7) = 1 because 7 is prime.
a(8) = 19 because 8 is not prime and prime(8) = 19.
		

Crossrefs

Cf. A007821, A010051, A061397, A191558.

Programs

Magma

[IsPrime(n) select 1 else NthPrime(n): n in [1..100]];

Mathematica

Table[If[PrimeQ[n], 1, Prime[n]], {n, 100}]