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 A083071 #5 Mar 04 2018 21:19:10 %S A083071 1,3,19,173,2001,28087,465011,8888889,192922993,4690709411, %T A083071 126370284195,3738060156613,120478742327009,4203359652212463, %U A083071 157854212399438371,6349779403743490289,272416890591642213921,12417347368421052631579 %N A083071 First subdiagonal of number array A083064. %F A083071 a(n) = ((n+1)*(n+3)^n + 1)/(n+2). %Y A083071 Cf. A083069, A083070. %K A083071 easy,nonn %O A083071 0,2 %A A083071 _Paul Barry_, Apr 21 2003