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 A284431 #12 Feb 06 2025 21:33:14 %S A284431 1,2,1,6,2,42,12,116,18,84,168,336,384,6864,7872,67392,52800,357120, %T A284431 115200,748800,3093120,11681280,26853120,43130880,74649600,2238382080, %U A284431 3588157440,51775856640,63188398080,653811056640,480220876800,4284050964480,1316818944000,11061279129600,76921038028800 %N A284431 The number of positive integer sequences of length n with no duplicate substrings of length greater than 1, every number different from its neighbors, and a minimal sum (= A282166(n)). %e A284431 For n = 5, the a(5) = 2 sequences are [1,3,1,2,1] and [1,2,1,3,1], each with a sum of A282166(5) = 8. %Y A284431 Cf. A282166, A283558, A284432, A284433, A284434. %K A284431 nonn %O A284431 1,2 %A A284431 _Peter Kagey_, Mar 27 2017 %E A284431 Terms a(9) onward from _Max Alekseyev_, Feb 06 2025