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 A145109 #15 Sep 05 2020 07:46:27 %S A145109 4,4,36,16,100,36,196,16,36,100,484,144,676,196,900,64,1156,36,1444, %T A145109 400,1764,484,2116,144,100,676,324,784,3364,900,3844,64,4356,1156, %U A145109 4900,144,5476,1444,6084,400,6724,1764,7396,1936,900,2116,8836,576,196,100,10404 %N A145109 a(n) = 2*n * core(2*n). %C A145109 All terms are even squares (A016742). %H A145109 Amiram Eldar, <a href="/A145109/b145109.txt">Table of n, a(n) for n = 1..10000</a> %F A145109 a(n) = A053143(2*n). - _Michel Marcus_, Aug 09 2013 %t A145109 a[1] = 4; a[n_] := 2*n * Times @@ (First[#]^Mod[Last[#], 2] & /@ FactorInteger[2*n]); Array[a, 50] (* _Amiram Eldar_, Sep 05 2020 *) %o A145109 (PARI) a(n) = 2*n * core(2*n); \\ _Michel Marcus_, Aug 09 2013 %Y A145109 Cf. A007913, A016742, A053143. %K A145109 easy,nonn %O A145109 1,1 %A A145109 _Reikku Kulon_, Oct 02 2008 %E A145109 Definition corrected by _Michel Marcus_, Aug 09 2013