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 A016886 #29 Feb 16 2025 08:32:33
%S A016886 9,64,169,324,529,784,1089,1444,1849,2304,2809,3364,3969,4624,5329,
%T A016886 6084,6889,7744,8649,9604,10609,11664,12769,13924,15129,16384,17689,
%U A016886 19044,20449,21904,23409,24964,26569,28224,29929,31684,33489,35344,37249,39204,41209
%N A016886 a(n) = (5*n + 3)^2.
%H A016886 Colin Barker, <a href="/A016886/b016886.txt">Table of n, a(n) for n = 0..1000</a>
%H A016886 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/PolygammaFunction.html">Polygamma Function</a>.
%H A016886 Wikipedia, <a href="http://en.wikipedia.org/wiki/Polygamma_function">Polygamma Function</a>.
%H A016886 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A016886 From _Colin Barker_, Mar 29 2017: (Start)
%F A016886 G.f.: (9 + x)*(1 + 4*x) / (1 - x)^3.
%F A016886 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>2.
%F A016886 (End)
%F A016886 a(n) = A000290(A016885(n)). - _Michel Marcus_, Mar 30 2017
%F A016886 Sum_{n>=0} 1/a(n) = polygamma(1, 3/5)/25. - _Amiram Eldar_, Oct 02 2020
%e A016886 a(0) = (5*0 + 3)^2 = 9.
%t A016886 (5*Range[0,40]+3)^2 (* or *) LinearRecurrence[{3,-3,1},{9,64,169},40] (* _Harvey P. Dale_, Dec 09 2016 *)
%t A016886 CoefficientList[Series[(9 + x) (1 + 4 x)/(1 - x)^3, {x, 0, 40}], x] (* _Michael De Vlieger_, Mar 29 2017 *)
%o A016886 (PARI) Vec((9 + x)*(1 + 4*x) / (1 - x)^3 + O(x^50)) \\ _Colin Barker_, Mar 29 2017
%o A016886 (Magma) [(5*n + 3)^2 : n in [0..50]]; // _Wesley Ivan Hurt_, Dec 02 2021
%Y A016886 Cf. A000290, A016885.
%K A016886 nonn,easy
%O A016886 0,1
%A A016886 _N. J. A. Sloane_