A086172 Numbers n such that n*prime(n)+1 is prime.

1, 2, 4, 6, 24, 30, 36, 42, 72, 84, 98, 100, 116, 126, 128, 144, 162, 174, 206, 212, 228, 288, 312, 318, 324, 336, 350, 360, 406, 408, 416, 418, 452, 458, 466, 498, 510, 522, 528, 530, 536, 546, 548, 556, 604, 654, 660, 666, 682, 684, 690, 708, 710, 728, 738

Offset: 1

Author

Zak Seidov, Jul 11 2003

Keywords

• easy
• nonn

Comments

See also A086173, A086174, A086175, A086176, A086177.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A086173, A086174, A086175, A086176, A086177.

Programs

Magma

[n: n in [1..800] | IsPrime(n*NthPrime(n) + 1)]; // Vincenzo Librandi, Oct 05 2012

Mathematica

Select[Range[1000], PrimeQ[ # Prime[ # ]+1]&]

PARI

is(n,p=prime(n))=isprime(n*p+1) \\ Charles R Greathouse IV, Feb 17 2017