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 A245428 #10 Jul 22 2014 12:35:31 %S A245428 10,30,100,330,1100,3670,12230,40770,135900,453000,1510000,5033330, %T A245428 16777770,55925900,186419660,621398870,2071329570,6904431900, %U A245428 23014773000,76715910000,255719700000,852399000000,2841330000000,9471100000000,31570333333330,105234444444430 %N A245428 Number of nonnegative integers with property that their base 10/3 expansion (see A024658) has n digits. %e A245428 a(2) = 30 because 30, 31,.., 60, 61, .., 98 and 99 are the base 10/3 expansions for the integers 10, 11, .., 20, 21,.., 38, and 39 respectively and these are the only integers with 2 digits. %o A245428 (Sage) %o A245428 A=[1] %o A245428 for i in [1..60]: %o A245428 A.append(ceil(((10-3)/3)*sum(A))) %o A245428 [10*x for x in A] %Y A245428 Cf. A024658, A081848, A245356. %K A245428 nonn,base %O A245428 1,1 %A A245428 _Hailey R. Olafson_, Jul 21 2014