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 A213539 #31 Oct 02 2017 08:02:22
%S A213539 1,2,4,5,7,8,10,11,14,16,19,20,22,23,28,29,31,32,35,37,38,40,44,46,47,
%T A213539 49,53,56,58,62,64,65,67,70,73,74,76,79,80,85,88,89,92,94,97,98,101,
%U A213539 103,106,112,116,119,121,124,125,128,130,131,133,134,140,143,146
%N A213539 Variant of numbers for which there is at least one 3-smooth representation that is special of level k.
%C A213539 These numbers are of the form 3^k*2^{a_0} + 3^{k-1}*2^{a_1} + ... + 3^1*2^{a_{k-1}} + 3^0*2^{a_k} in which every power 3^i appears, 0 <= i <= k, and where a_i satisfies 0 <= a_0 < a_1 < ... < a_k.
%C A213539 These values are those of sequence A116640 in addition to any multiple of two of elements of this sequence. - _Kenneth Vollmar_, Jun 05 2013
%D A213539 Kenneth Vollmar, Recursive calculation of 3-smooth representations special of level k, To be submitted mid-2013.
%H A213539 R. Blecksmith, M. McCallum and J. L. Selfridge, <a href="http://www.jstor.org/stable/2589404">3-smooth representations of integers</a>, Amer. Math. Monthly, 105 (1998), 529-543.
%e A213539 n=19 has two 3-smooth representations that are special of level k. At k=1, 19 = 3^1*2^0 + 3^0*2^4. At k=2, 19 = 3^2*2^0 + 3^1*2^1 + 3^0*2^2.
%Y A213539 Cf. A116623, A116640, A116641, A119733, A226383, A003586.
%K A213539 nonn
%O A213539 0,2
%A A213539 _Kenneth Vollmar_, Mar 03 2013
%E A213539 Corrected a reference to another sequence and added cross references - _Joe Slater_, Dec 19 2016