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 A158056 #25 Sep 08 2022 08:45:42
%S A158056 18,68,150,264,410,588,798,1040,1314,1620,1958,2328,2730,3164,3630,
%T A158056 4128,4658,5220,5814,6440,7098,7788,8510,9264,10050,10868,11718,12600,
%U A158056 13514,14460,15438,16448,17490,18564,19670,20808,21978,23180,24414,25680
%N A158056 a(n) = 16*n^2 + 2*n.
%C A158056 The identity (16*n + 1)^2 - (16*n^2 + 2*n)*4^2 = 1 can be written as A158057(n)^2 - a(n)*4^2 = 1. - _Vincenzo Librandi_, Feb 09 2012
%C A158056 Sequence found by reading the line from 18, in the direction 18, 68, ... in the square spiral whose vertices are the generalized decagonal numbers A074377. - _Omar E. Pol_, Nov 02 2012
%H A158056 Vincenzo Librandi, <a href="/A158056/b158056.txt">Table of n, a(n) for n = 1..10000</a>
%H A158056 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A158056 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
%F A158056 G.f.: 2*x*(-9 - 7*x)/(x-1)^3.
%t A158056 LinearRecurrence[{3,-3,1},{18,68,150},50]
%t A158056 Table[16n^2+2n,{n,40}] (* _Harvey P. Dale_, Apr 13 2011 *)
%o A158056 (Magma) I:=[18, 68, 150]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
%o A158056 (PARI) a(n) = 16*n^2 + 2*n.
%Y A158056 Cf. A158057.
%K A158056 nonn,easy
%O A158056 1,1
%A A158056 _Vincenzo Librandi_, Mar 12 2009