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 A081345 #19 Sep 08 2022 08:45:09
%S A081345 1,4,5,16,17,36,37,64,65,100,101,144,145,196,197,256,257,324,325,400,
%T A081345 401,484,485,576,577,676,677,784,785,900,901,1024,1025,1156,1157,1296,
%U A081345 1297,1444,1445,1600,1601,1764,1765,1936,1937,2116,2117,2304,2305,2500
%N A081345 First row in maze arrangement of natural numbers A081344.
%H A081345 Vincenzo Librandi, <a href="/A081345/b081345.txt">Table of n, a(n) for n = 0..1000</a>
%H A081345 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A081345 a(n) = n^2 + n + 1 - n*(-1)^n = n^2 + n + 1 + n*(-1)^(n+1).
%F A081345 a(2*n) = A053755(n), a(2*n+1) = 4 * A004120(n).
%F A081345 G.f.: (5*x^3-x^2+3*x+1)/((1-x)^3*(1+x)^2). [_Colin Barker_, Sep 03 2012]
%t A081345 CoefficientList[Series[(5 x^3 - x^2 + 3 x + 1) / ((1 - x)^3 (1 + x)^2), {x, 0, 50}], x] (* _Vincenzo Librandi_, Aug 08 2013 *)
%o A081345 (Magma) [n^2+n+1-n*(-1)^n: n in [0..50]]; // _Vincenzo Librandi_, Aug 08 2013
%Y A081345 Cf. A081346.
%K A081345 easy,nonn
%O A081345 0,2
%A A081345 _Paul Barry_, Mar 19 2003