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 A027091 #9 May 04 2025 15:43:45 %S A027091 1,1,5,17,54,169,517,1559,4653,13787,40638,119333,349469,1021433, %T A027091 2981330,8693467,25333627,73795263,214915073,625855927,1822630172, %U A027091 5308552227,15464475465,45060652609,131334677147,382907083385 %N A027091 a(n) = A027082(n, 2n-4). %Y A027091 Cf. A027082. %K A027091 nonn %O A027091 2,3 %A A027091 _Clark Kimberling_