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 A081249 #9 Sep 21 2016 11:28:41
%S A081249 0,1,1,2,4,7,9,10,10,11,13,16,20,25,31,38,46,55,63,70,76,81,85,88,90,
%T A081249 91,91,92,94,97,101,106,112,119,127,136,146,157,169,182,196,211,227,
%U A081249 244,262,281,301,322,344,367,391,416,442,469,495,520,544,567,589,610,630
%N A081249 Partial sums of A081134.
%H A081249 Klaus Brockhaus, <a href="/A081134/a081134.gif">Illustration for A081134, A081249, A081250 and A081251</a>
%F A081249 a(n) = sum{j=1..n, A081134(j)}.
%e A081249 First seven terms of A081134 are 0,1,0,1,2,3,2, so a(7) = 9.
%t A081249 Accumulate[Flatten[Table[Join[Range[0,3^n],Range[3^n-1,1,-1]],{n,0,4}]]] (* _Harvey P. Dale_, Sep 21 2016 *)
%o A081249 (PARI) {s=0; for(n=1,62,p=3^floor(0.1^25+log(n)/log(3)); print1(s=s+min(n-p,3*p-n),","))}
%K A081249 easy,nonn
%O A081249 1,4
%A A081249 _Klaus Brockhaus_, Mar 17 2003