A154432 Numbers k such that 5k^2-k+1 is prime.

1, 2, 3, 7, 8, 9, 10, 12, 14, 17, 19, 22, 24, 29, 33, 35, 42, 43, 50, 52, 57, 58, 65, 68, 72, 73, 75, 77, 94, 99, 105, 107, 117, 119, 120, 124, 129, 138, 140, 143, 155, 162, 178, 184, 187, 189, 190, 194, 199, 204, 208, 210, 219, 220, 229, 245, 248, 250, 252, 254, 255

Offset

1,2

Links

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

Example

The associated primes are p=5 for n=1, p=19 for n=2, p=43 for n=3, p=239 for n=7.

Maple

for n from 1 to 3000 do p := 5*n^2-n+1 ; if isprime(p) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Jan 12 2009

Mathematica

Select[Range[0, 300], PrimeQ[5*#^2 -# +1]&] (* Vincenzo Librandi, Sep 24 2012 *)

Prog

(Magma) [n: n in [0..300] | IsPrime(5*n^2 - n + 1)]; // Vincenzo Librandi, Sep 24 2012
(PARI) is(n)=isprime(5*n^2-n+1) \\ Charles R Greathouse IV, Sep 24 2012

Crossrefs

Cf. A154431.

Sequence in context: A326874 A118374 A344624 * A251391 A047361 A037461

Adjacent sequences: A154429 A154430 A154431 * A154433 A154434 A154435

Keyword

nonn,easy

Author

Vincenzo Librandi, Jan 09 2009

Extensions

114 removed; extended by R. J. Mathar, Jan 12 2009

Misleading formula removed by R. J. Mathar, Jul 24 2009

Status

approved