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 A293750 #39 Jul 23 2018 02:46:33 %S A293750 0,2,4,6,10,12,18,20,26,30,36,38,46,48,54,62,72,74,84,86,96,104,110, %T A293750 112,124,130,136,144,158,160 %N A293750 a(n) is the total number of line segments that belong to the Dyck paths in the diagram of the symmetries of sigma described in A236104 and A237593 after n-th stage, with a(0) = 0. %F A293750 a(n) = A294847(n) - 2. %e A293750 Illustration of initial terms (n = 1..6): %e A293750 . _ _ _ _ %e A293750 . _ _ _ _ _ _ |_ %e A293750 . _ _ _ _ _ _| _ _ _| |_ %e A293750 . _ _ _ _ |_ _ _ |_ _ _ _ |_ _ | %e A293750 . _ _ _ _|_ _ _|_ | _ _|_ | | _ _|_ | | | %e A293750 . _ _ | _ | | _ | | | _ | | | | _ | | | | | %e A293750 . | | | | | | | | | | | | | | | | | | | | | %e A293750 . %e A293750 . 2 4 6 10 12 18 %e A293750 . %Y A293750 Cf. A000203, A024916, A196020, A235791, A236104, A237048, A237270, A237271, A237590, A237591, A237593, A245092, A262626, A294723, A294847. %K A293750 nonn,more %O A293750 0,2 %A A293750 _Omar E. Pol_, Nov 09 2017