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 A175006 #8 Sep 08 2018 14:51:17
%S A175006 1,3,9,21,44,81,139,222,339,495,701,963,1294,1701,2199,2796,3509,4347,
%T A175006 5329,6465,7776,9273,10979,12906,15079,17511,20229,23247,26594,30285,
%U A175006 34351,38808,43689,49011,54809,61101,67924,75297,83259,91830,101051,110943,121549,132891
%N A175006 Row sums of triangle A175009.
%H A175006 Andrew Howroyd, <a href="/A175006/b175006.txt">Table of n, a(n) for n = 1..1000</a>
%H A175006 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,-5,5,1,-3,1)
%F A175006 From _Andrew Howroyd_, Sep 01 2018: (Start)
%F A175006 a(n) = n + Sum{k=1..n} (n-k+1)*(binomial(k+1, 2) - binomial(floor(k/2)+1, 2) - 1).
%F A175006 a(n) = 3*a(n-1) - a(n-2) - 5*a(n-3) + 5*a(n-4) + a(n-5) - 3*a(n-6) + a(n-7) for n > 7.
%F A175006 G.f.: x*(1 + x^2 + 2*x^3 - x^5)/((1 - x)^5*(1 + x)^2).
%F A175006 (End)
%e A175006 a(4) = 21 = (1 + 4 + 9 + 7), where (1, 4, 9, 7) = row 4 of triangle A175009.
%o A175006 (PARI) Vec((1 + x^2 + 2*x^3 - x^5)/((1 - x)^5*(1 + x)^2) + O(x^50)) \\ _Andrew Howroyd_, Sep 01 2018
%Y A175006 Cf. A175009, A026741, A001318
%K A175006 nonn,easy
%O A175006 1,2
%A A175006 _Gary W. Adamson_, Apr 03 2010
%E A175006 Duplicate term removed and a(15) and beyond from _Andrew Howroyd_, Sep 01 2018