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 A081346 #15 Sep 08 2022 08:45:09 %S A081346 1,2,9,10,25,26,49,50,81,82,121,122,169,170,225,226,289,290,361,362, %T A081346 441,442,529,530,625,626,729,730,841,842,961,962,1089,1090,1225,1226, %U A081346 1369,1370,1521,1522,1681,1682,1849,1850,2025,2026,2209,2210,2401,2402,2601 %N A081346 First column in maze arrangement of natural numbers A081344. %C A081346 Interleaves odd squares A016754 with central polygonal numbers A001844. %H A081346 Vincenzo Librandi, <a href="/A081346/b081346.txt">Table of n, a(n) for n = 0..10000</a> %H A081346 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1). %F A081346 a(n) = n^2 + n + 1 + n*(-1)^n. %F A081346 a(2*n) = A016754(n), a(2*n+1) = 2*A001844(n). %F A081346 G.f.: (1 + x + 5*x^2 - x^3 + 2*x^4)/((1-x)^3*(1+x)^2). [_Colin Barker_, Sep 03 2012] %o A081346 (Magma) [n^2+n+1+n*(-1)^n: n in [0..50]]; // _Vincenzo Librandi_, Sep 05 2011 %Y A081346 Cf. A081345. %K A081346 easy,nonn %O A081346 0,2 %A A081346 _Paul Barry_, Mar 19 2003