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A322422 Numbers k such that the sum of the first k*(k+1) primes is prime. 3
1, 2, 3, 11, 18, 31, 34, 49, 57, 76, 79, 84, 97, 118, 139, 140, 172, 175, 183, 184, 185, 191, 208, 218, 221, 232, 233, 247, 262, 266, 294, 313, 315, 323, 333, 334, 339, 344, 351, 361, 366, 372, 407, 413, 436, 445, 461, 473, 478, 500, 545, 546, 556, 564, 577 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Ray Chandler, Table of n, a(n) for n = 1..1000

FORMULA

A322421(n) = A322420(a(n)) = A007504(A002378(a(n))).

MATHEMATICA

f[n_] := Sum[Prime[k], {k, n}]; Select[Range[500],

PrimeQ[f[#*(# + 1)]] &]

CROSSREFS

Cf. A002378, A007504, A322420, A322421.

Sequence in context: A263938 A263932 A267420 * A024861 A025101 A025105

Adjacent sequences:  A322419 A322420 A322421 * A322423 A322424 A322425

KEYWORD

nonn

AUTHOR

Ray Chandler, Dec 07 2018

STATUS

approved

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Last modified July 25 18:32 EDT 2021. Contains 346291 sequences. (Running on oeis4.)