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 A231960 #18 Feb 28 2014 13:07:07 %S A231960 1,3,6,9,12,18,24,27,30,36,42,48,54,60,66,72,78,81,84,90,96,102,108, %T A231960 114,120,126,132,138,144,150,156,162,168,174,180,186,192,198,204,210, %U A231960 216,222,228,234,240,243,246,252,258 %N A231960 Powers of 3 together with multiples of 6. %C A231960 Union of A000244 and A008588 (without 0). %C A231960 Also, 1 and 3*(even numbers (A005843) UNION powers of 3 (A008588)). %C A231960 Also, numbers m such that m divides A057083(m-1), see the Smyth reference. %H A231960 C. Smyth, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL13/Smyth/smyth2.html">The Terms in Lucas Sequences Divisible by their Indices</a>, Journal of Integer Sequences, Vol.13 (2010), Article 10.2.4. %o A231960 (Sage) def is_in_A231960(n): %o A231960 return 6.divides(n) or n==3^valuation(n,3) %Y A231960 Cf. A029744. %K A231960 nonn %O A231960 1,2 %A A231960 _Thomas M. Bridge_, Nov 15 2013 %E A231960 Edited by _Ralf Stephan_, Feb 28 2014