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 A245425 #9 Jul 22 2014 22:18:51 %S A245425 9,18,36,81,180,405,918,2061,4635,10431,23472,52812,118827,267363, %T A245425 601560,1353510,3045402,6852150,15417342,34689015,78050286,175613148, %U A245425 395129583,889041555,2000343501,4500772875,10126738971,22785162687,51266616048,115349886108 %N A245425 Number of nonnegative integers with the property that their base 9/4 expansion (see A024652) has n digits. %e A245425 The numbers 9-26 are represented by 40, 41, 42, 43, 44, 45, 46, 47, 48, 80, 81, 82, 83, 84, 85, 86, 87, 88 respectively in base 9/4. Since these are the only two digit integers we have a(2) = 18. %o A245425 (Sage) %o A245425 A=[1] %o A245425 for i in [1..100]: %o A245425 A.append(ceil(((9-4)/4)*sum(A))) %o A245425 [9*x for x in A] %Y A245425 Cf. A024652, A245356, A081848. %K A245425 nonn,base %O A245425 1,1 %A A245425 _Tom Edgar_, Jul 21 2014