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 A174012 #11 Jul 01 2020 14:35:16 %S A174012 0,6,3,18,6,30,9,42,12,54,15,66,18,78,21,90,24,102,27,114,30,126,33, %T A174012 138,36,150,39,162,42,174,45,186,48,198,51,210,54,222,57,234,60,246, %U A174012 63,258,66,270,69,282,72,294,75,306,78,318,81,330,84,342,87,354,90,366,93,378,96 %N A174012 a(n) = 3 * A064680(n). %F A174012 a(n) = A064680(3*n), similar to A165988. %F A174012 a(n) mod 9 = 3*A080425(n) (period length 3). %F A174012 a(2n+1) = A017593(n). %F A174012 a(2n) = A008585(n). %Y A174012 Cf. A008585, A017593, A064680, A080425, A165988. %K A174012 nonn,easy %O A174012 0,2 %A A174012 _Paul Curtz_, Mar 05 2010 %E A174012 a(0) = 0 prepended by _Georg Fischer_, Jul 01 2020