A055472 Primes of the form k(k+1)/2+2 (i.e., two more than a triangular number).

2, 3, 5, 17, 23, 47, 107, 173, 233, 353, 467, 563, 743, 863, 1277, 1433, 1487, 2213, 2417, 2777, 3083, 3323, 4007, 4373, 5153, 7877, 8387, 10733, 11177, 11783, 13043, 13697, 14537, 15053, 15227, 17207, 17393, 17957, 18917, 21323, 22157, 23873

Offset

1,1

Comments

Equal to primes of the form (k^2+15)/8. Also equal to primes p such that 8*p-15 is a square. - Chai Wah Wu, Jul 14 2014

Primes of A152948. - Klaus Purath, Jan 03 2021

Links

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

Mathematica

Select[Table[(n^2-n+4)/2, {n, 3000}], PrimeQ] (* Vincenzo Librandi, Jul 14 2012 *)
Select[Accumulate[Range[0, 300]]+2, PrimeQ] (* Harvey P. Dale, Feb 05 2019 *)

Prog

(Python)
import sympy
[n*(n+1)/2+2 for n in range(10**6) if sympy.ntheory.primetest.isprime(n*(n+1)/2+2)] # Chai Wah Wu, Jul 14 2014

Crossrefs

Cf. A000040, A000217, A022856, A152948.

Sequence in context: A155978 A235925 A106859 * A077499 A127061 A215311

Adjacent sequences: A055469 A055470 A055471 * A055473 A055474 A055475

Keyword

nonn

Author

Henry Bottomley, Jun 27 2000

Status

approved