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 A291780 #12 Jul 12 2018 08:07:55 %S A291780 2,4,4,4,16,32,64,128,128,320,1152,1792,3584,8704,16384,28672,65536, %T A291780 118784,221184,483328,851968,1720320,3866624,6815744,14483456, %U A291780 31719424,55574528,113770496,246939648,438304768,837812224,1790967808,3309305856 %N A291780 Consider the Watanabe tag system defined in A291067; a(n) = number of binary words of length n which terminate at the empty word. %H A291780 Don Reble, <a href="/A291780/b291780.txt">Table of n, a(n) for n = 1..60</a> %Y A291780 Cf. A284116, A291067, A291781. %K A291780 nonn %O A291780 1,1 %A A291780 _Don Reble_ and _N. J. A. Sloane_, Sep 01 2017