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 A248381 #7 Oct 12 2014 21:18:06 %S A248381 9,15,27,57,81,177,243,393,579,729,849,1257,2187,4197,4143,5853,6561, %T A248381 17817,17781,19683,56157,59049,104289,104277,154509 %N A248381 Multiples of 3 in A247665 in order of appearance. %C A248381 The initial multiples of 3 occur at positions 6,13,28,57,115,231, ... - conjecturally, for n > 13, A247665(n) is a multiple of 3 iff n = 29*2^k-1, k >= 0. %e A248381 Table showing index where multiples of 3 appear, the multiple of 3, and the number of different prime factors of that term: %e A248381 6 9 1 %e A248381 13 15 2 %e A248381 28 27 1 %e A248381 57 57 2 %e A248381 115 81 1 %e A248381 231 177 2 %e A248381 463 243 1 %e A248381 927 393 2 %e A248381 1855 579 2 %e A248381 3711 729 1 %e A248381 7423 849 2 %e A248381 14847 1257 2 %e A248381 29695 2187 1 %e A248381 59391 4197 2 %e A248381 118783 4143 2 %e A248381 237567 5853 2 %e A248381 475135 6561 1 %e A248381 950271 17817 2 %e A248381 1900543 17781 2 %e A248381 3801087 19683 1 %e A248381 7602175 56157 2 %e A248381 15204351 59049 1 %e A248381 30408703 104289 2 %e A248381 60817407 104277 2 %e A248381 121634815 154509 2 %Y A248381 Cf. A247665, A248379 (multiples of 2). %K A248381 nonn,more %O A248381 1,1 %A A248381 _Russ Cox_ and _N. J. A. Sloane_, Oct 12 2014