A275059 Numbers n such that A000010(n) + n^2 is a prime.

1, 2, 3, 5, 11, 13, 15, 19, 31, 33, 35, 41, 51, 53, 59, 65, 83, 89, 91, 101, 103, 115, 131, 141, 149, 161, 163, 181, 185, 187, 191, 193, 199, 217, 221, 233, 241, 263, 281, 287, 295, 303, 329, 331, 349, 373, 401, 415, 419, 431, 433, 445, 449, 461, 463, 469, 473, 499, 517

Offset: 1

Author

Vincenzo Librandi, Jul 27 2016

Keywords

• nonn
• easy

Comments

For n >= 2, a(n) is odd and squarefree. - Robert Israel, Jul 29 2016

Examples

			5 is a term because A000010(5) + 5^2 = 29 is a prime number.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A259145.

Programs

Magma

[n: n in [1..800] | IsPrime(n^2+EulerPhi(n))];

Maple

select(t -> isprime(numtheory:-phi(t) + t^2), [1,2,seq(n,n=3..1000,2)]); # Robert Israel, Jul 29 2016

Mathematica

Select[Range[2000], PrimeQ[#^2 + EulerPhi[#]] &]

PARI

isok(n) = isprime(eulerphi(n) + n^2); \\ Altug Alkan, Jul 27 2016