A171570 Triangular numbers T such that T+2 is a prime.
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
Offset: 1
Keywords
Examples
1+2=3, 3+2=5, 15+2=17, ..
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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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 *)