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 A255186 #28 Feb 06 2023 06:06:17
%S A255186 0,1,27,78,154,255,381,532,708,909,1135,1386,1662,1963,2289,2640,3016,
%T A255186 3417,3843,4294,4770,5271,5797,6348,6924,7525,8151,8802,9478,10179,
%U A255186 10905,11656,12432,13233,14059,14910,15786,16687,17613,18564,19540
%N A255186 27-gonal numbers: a(n) = n*(25*n-23)/2.
%C A255186 See comments in A255184.
%D A255186 E. Deza and M. M. Deza, Figurate numbers, World Scientific Publishing (2012), page 6 (25th row of the table).
%H A255186 Luciano Ancora, <a href="/A255186/b255186.txt">Table of n, a(n) for n = 0..1000</a>
%H A255186 <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>
%H A255186 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A255186 G.f.: x*(-1 - 24*x)/(-1 + x)^3.
%F A255186 a(n) = A000217(n) + 24*A000217(n-1).
%F A255186 Product_{n>=2} (1 - 1/a(n)) = 25/27. - _Amiram Eldar_, Jan 22 2021
%F A255186 E.g.f.: exp(x)*(x + 25*x^2/2). - _Nikolaos Pantelidis_, Feb 06 2023
%t A255186 Table[n (25 n - 23)/2, {n, 40}]
%o A255186 (PARI) a(n)=n*(25*n-23)/2 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A255186 Cf. similar sequences listed in A255184.
%K A255186 nonn,easy
%O A255186 0,3
%A A255186 _Luciano Ancora_, Apr 04 2015