This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A115882 #11 Jul 15 2021 21:23:03 %S A115882 1,20,49,65,103,176,279,284,299,437,513,553,656,973,1271,1779,1921, %T A115882 2156,2312,2347,2554,2759,3176,3379,4008,4028,4132,5255,6354,6764, %U A115882 7116,8299,8334,8366,8723,9277,9755,10092,10475,10631,11429,11842,12633,13157,13627 %N A115882 Numbers k such that k + prime(k) gives a triangular number. %H A115882 T. D. Noe, <a href="/A115882/b115882.txt">Table of n, a(n) for n = 1..1000</a> %e A115882 103 + prime(103) = 103 + 563 = 666 = T(36). %t A115882 TriangularQ[n_] := IntegerQ[Sqrt[1 + 8*n]]; Select[Range[20000], TriangularQ[# + Prime[#]] &] (* _T. D. Noe_, Jan 27 2014 *) %o A115882 (PARI) isok(n) = ispolygonal(n + prime(n), 3); \\ _Michel Marcus_, Jan 25 2014 %Y A115882 Cf. A064371, A115883, A115886. %K A115882 nonn %O A115882 1,2 %A A115882 _Giovanni Resta_, Feb 06 2006