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 A125770 #10 Nov 28 2024 13:28:10
%S A125770 1,2,7,9,34,31,54,15,16,26,148,68,398,62,193,25,27,140,550,397,107,
%T A125770 113,50,122,950,226,38,169,40,562,187,44,327,763,70,211,362,49,1726,
%U A125770 79,394,153,55,202,1600,125,61,419,94,95,225,98,66,1036,508,1298,983,69,71
%N A125770 First occurrence of n in A125769.
%C A125770 If we restrict ourselves to just j*T_k +1 or j*T_k -1 then there are values which do not occur. As an example if the minus is used then 8 and 9 are missing.
%t A125770 triQ[n_] := IntegerQ@ Sqrt[8*n + 1]; f[n_] := Block[{j = 1, p = Prime@n}, While[ !triQ[(p - 1)/j] && !triQ[(p + 1)/j], j++ ]; j]; t = Table[0, {100}]; Do[ a = f@n; If[a < 101 && t[[a]] == 0, t[[a]] = n; Print[{a, n}]], {n, 3500}]; t
%Y A125770 A125769 = a(n) is the least number j such that j*T_k +/- 1 is n-th prime for some k-th triangular number.
%Y A125770 Cf. A000217, A125765, A125766, A125767, A125768, A125769.
%K A125770 nonn
%O A125770 1,2
%A A125770 _Jonathan Vos Post_ and _Robert G. Wilson v_, Dec 03 2006