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 A181959 #25 Apr 11 2012 09:57:18 %S A181959 9,48,236,1274,6489,30229,142320,711955,3601566 %N A181959 Number of distinct integers that can be generated by an expression containing n binary operators (any of add, subtract, multiply and divide) whose operands are any integer between 1 and 9; parenthesis allowed. %H A181959 Derek M. Jones, <a href="/A181959/a181959_1.r.txt">R program to generate list</a> %H A181959 <a href="/index/Com#complexity">Index to sequences related to the complexity of n</a> %e A181959 a(1)=48, the distinct values are -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 20 21 24 25 27 28 30 32 35 36 40 42 45 48 49 54 56 63 64 72 81 %Y A181959 Cf. A181898, A181957, A181958, A181960. %K A181959 nonn %O A181959 0,1 %A A181959 _Derek M. Jones_, Apr 03 2012