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 A027122 #7 Oct 23 2019 20:34:52 %S A027122 1,2,7,24,77,241,738,2227,6650,19711,58114,170682,499911,1461284, %T A027122 4265437,12438449,36247956,105589899,307513742,895514715,2607925982, %U A027122 7595726764,22127052759,64473303788,187912261301,547850119836 %N A027122 a(n) = A027113(n, 2n-4). %K A027122 nonn %O A027122 2,2 %A A027122 _Clark Kimberling_