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A055472 Primes of the form k(k+1)/2+2 (i.e., two more than a triangular number). 7
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 (list; graph; refs; listen; history; text; internal format)
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

LINKS

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

MAPLE

P:=proc(n) local i, w; w:=2; for i from 0 by 1 to n do w:=w+i; if isprime(w) then print(w); fi; od; end: P(1000); # Paolo P. Lava, Apr 24 2007

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.

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

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Last modified February 28 23:19 EST 2020. Contains 332353 sequences. (Running on oeis4.)