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 A081553 #7 May 29 2021 20:05:10
%S A081553 1,21,303,4006,50010,600015,7000021,80000028,900000036,10000000045,
%T A081553 110000000055,1200000000066,13000000000078,140000000000091,
%U A081553 1500000000000105,16000000000000120,170000000000000136,1800000000000000153,19000000000000000171,200000000000000000190,2100000000000000000210,22000000000000000000231
%N A081553 Sum of n-th row of A081551.
%H A081553 G. C. Greubel, <a href="/A081553/b081553.txt">Table of n, a(n) for n = 1..500</a>
%H A081553 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (23,-163,361,-320,100).
%F A081553 a(n) = n*10^(n-1) + n*(n-1)/2.
%F A081553 From _G. C. Greubel_, May 27 2021: (Start)
%F A081553 G.f.: x*(1 -2*x -17*x^2 +99*x^3)/((1-x)^3 * (1-10*x)^2).
%F A081553 E.g.f.: (1/2)*x*( x*exp(x) + 2*exp(10*x) ). (End)
%t A081553 Table[n*10^(n-1) +n(n-1)/2, {n,40}] (* _G. C. Greubel_, May 27 2021 *)
%o A081553 (Sage) [n*10^(n-1) +binomial(n,2) for n in (1..40)] # _G. C. Greubel_, May 27 2021
%Y A081553 Cf. A081551, A081552.
%Y A081553 Cf. A126431, A161680.
%K A081553 base,easy,nonn
%O A081553 1,2
%A A081553 _Amarnath Murthy_, Apr 01 2003
%E A081553 Terms a(13) onward added by _G. C. Greubel_, May 27 2021