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 A049509 #18 Mar 01 2021 07:44:38 %S A049509 4,7,12,15,19,25,28,31,33,37,39,45,49,55,59,63,66,68,69,73,78,88,91, %T A049509 93,101,102,106,107,111,113,118,123,129,134,138,139,144,148,151,154, %U A049509 155,159,161,163,165,168,181,184,187,195,199,203,206,211,214,217,219,225 %N A049509 Numbers k such that prime(k) == 7 (mod 10). %C A049509 The asymptotic density of this sequence is 1/4 (by Dirichlet's theorem). - _Amiram Eldar_, Mar 01 2021 %F A049509 a(n) = A000720(A030432(n)). - _Ray Chandler_, Nov 07 2006 %t A049509 Select[Range[240], Mod[Prime[ # ], 10] == 7 &] (* _Ray Chandler_, Nov 07 2006 *) %Y A049509 Cf. A000720, A030432, A102342. %Y A049509 Cf. A049508, A049510, A049511. %K A049509 nonn %O A049509 1,1 %A A049509 _N. J. A. Sloane_ %E A049509 Extended by _Ray Chandler_, Nov 07 2006