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 A376205 #7 Sep 15 2024 22:04:43 %S A376205 2,31,59,67,79,83,101,103,109,113,127,137,139,151,173,181,191,199,227, %T A376205 229,239,241,263,283,293,311,317,331,347,349,353,367,373,379,383,397, %U A376205 421,433,449,461,463,479,487,491,499,523,547,557,563,569,577,587,593,599 %N A376205 Prime indices of triangular numbers k such that k + 1 and k - 2 are not prime. %D A376205 David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987. See entry 496 at p. 155. %e A376205 31 is a term since it is prime and both A000217(31) + 1 = 497 and A000217(31) - 2 = 494 are not prime. %t A376205 Select[Range[600], PrimeQ[#]&&!PrimeQ[t=#(#+1)/2+1]&&!PrimeQ[t-3] &] %Y A376205 Cf. A000040 (supersequence), A000124, A000217, A034856. %Y A376205 Complement of A376206 in A000040. %K A376205 nonn,easy %O A376205 1,1 %A A376205 _Stefano Spezia_, Sep 15 2024