A154619 Primes of the form (4k^2 + 4k - 5)/5.

23, 71, 167, 191, 479, 743, 1583, 2039, 2927, 3863, 5711, 6551, 7919, 9767, 10487, 11423, 15791, 16703, 18119, 21647, 21911, 24359, 27527, 32159, 35111, 35447, 38543, 43991, 45887, 46271, 52223, 54287, 55967, 60719, 67511, 69383, 76631

Offset: 1

Author

Vincenzo Librandi, Jan 16 2009

Keywords

• nonn
• easy

Comments

The numbers k that generate integers of the form (4k^2 + 4k - 5)/5 are in A047208. The primes are generated by the subset k = 5, 9, 14, 15, 24, 30, ... of these. - R. J. Mathar, Jan 25 2009

Links

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

Crossrefs

Cf. A028880.

Programs

Maple

a := proc (n) if type((4/5)*n^2+(4/5)*n-1, integer) = true and isprime((4/5)*n^2+(4/5)*n-1) = true then (4/5)*n^2+(4/5)*n-1 else end if end proc: seq(a(n), n = 1 .. 340); # Emeric Deutsch, Jan 21 2009

Mathematica

Select[Table[(4n^2+4n-5)/5,{n,3,200}],PrimeQ] (* Vincenzo Librandi, Jul 23 2012 *)

Extensions

Definition corrected and more terms from R. J. Mathar and Omar E. Pol, Jan 24 2009

Extended by Emeric Deutsch, Jan 21 2009