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 A274008 #11 Oct 11 2022 14:10:58 %S A274008 1,3,7,15,27,47,71,107,151,207,271,355,447,563,691,835,995,1187,1391, %T A274008 1631,1887,2167,2467,2811,3171,3571,3995,4455,4939,5479,6035,6651, %U A274008 7299,7987,8707,9475,10267,11131,12031,12979,13959,15019,16103,17271,18479,19735 %N A274008 Number of length-n ternary sequences where the sum of each block differs by at most 1 from every other block of the same length. %F A274008 a(n) = 2*A005598(n) - 1. - _Rémy Sigrist_, Oct 11 2022 %e A274008 For n = 2 the only strings omitted are 02 and 20. %Y A274008 Cf. A005598, which is the analogous sequence where "ternary" is replaced by "binary". %Y A274008 Cf. A274005, which is the analogous sequence where "ternary" is replaced by "binary" and "1" is replaced by "2". %K A274008 nonn %O A274008 0,2 %A A274008 _Jeffrey Shallit_, Jun 06 2016 %E A274008 More terms from _Rémy Sigrist_, Oct 11 2022