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 A334320 #18 Jul 03 2021 10:37:39 %S A334320 0,0,1,1,5,6,13,15,25,28,41,45,61,66,85,91,113,120,145,153,181,190, %T A334320 221,231,265,276,313,325,365,378,421,435,481,496,545,561,613,630,685, %U A334320 703,761,780,841,861,925,946,1013,1035,1105,1128,1201,1225,1301,1326,1405 %N A334320 Number of even integers in base n with exactly two distinct digits. %H A334320 Alois P. Heinz, <a href="/A334320/b334320.txt">Table of n, a(n) for n = 0..10000</a> %H A334320 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1). %F A334320 G.f.: -(x^3+2*x^2+1)*x^2/((x+1)^2*(x-1)^3). %F A334320 a(n) = A334318(n,2). %e A334320 a(4) = 5: 10, 12, 20, 30, 32 (written in base 4). %e A334320 a(7) = 15: 13, 15, 20, 24, 26, 31, 35, 40, 42, 46, 51, 53, 60, 62, 64 (written in base 7). %Y A334320 Column k=2 of A334318. %K A334320 nonn,easy %O A334320 0,5 %A A334320 _Alois P. Heinz_, Apr 22 2020