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A171570 Triangular numbers T such that T+2 is a prime. 1
1, 3, 15, 21, 45, 105, 171, 231, 351, 465, 561, 741, 861, 1275, 1431, 1485, 2211, 2415, 2775, 3081, 3321, 4005, 4371, 5151, 7875, 8385, 10731, 11175, 11781, 13041, 13695, 14535, 15051, 15225, 17205, 17391, 17955, 18915, 21321, 22155, 23871, 24531 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

1+2=3, 3+2=5, 15+2=17,..

MATHEMATICA

Select[s=0; Table[n*(n+1)/2, {n, 6!}], PrimeQ[ #+2]&]

Select[Accumulate[Range[300]], PrimeQ[#+2]&] (* Harvey P. Dale, Jun 27 2017 *)

CROSSREFS

Cf. A000217, A129545, A129752, A171569

Sequence in context: A014493 A147025 A147017 * A076825 A259745 A118565

Adjacent sequences:  A171567 A171568 A171569 * A171571 A171572 A171573

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 11 2009

STATUS

approved

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Last modified October 26 13:09 EDT 2021. Contains 348267 sequences. (Running on oeis4.)