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 A245417 #6 Jul 22 2014 22:18:10 %S A245417 7,14,28,70,161,378,882,2058,4802,11200,26138,60984,142296,332024, %T A245417 774725,1807694,4217948,9841881,22964389,53583572,125028337,291732784, %U A245417 680709834,1588322946,3706086874,8647536037,20177584084,47081029534,109855735577,256330049682 %N A245417 Number of nonnegative integers with property that their base 7/3 expansion (see A024640) has n digits. %e A245417 The only integers requiring two digits in base 7/3 are 30, 31, 32, 33, 34, 35, 36, 60, 61, 62, 63, 64, 65, 66, representing 7-20 respectively; thus, a(2) = 14. %o A245417 (Sage) %o A245417 A=[1] %o A245417 for i in [1..100]: %o A245417 A.append(ceil(((7-3)/3)*sum(A))) %o A245417 [7*x for x in A] %Y A245417 Cf. A245356, A081848, A024640. %K A245417 nonn,base %O A245417 1,1 %A A245417 _Tom Edgar_, Jul 21 2014