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 A282170 #12 Feb 05 2025 22:07:43 %S A282170 1,2,6,6,24,48,120,240,1440,2880,10080,20160,120960,322560,1209600, %T A282170 2903040,17418240,58060800,174182400,638668800,3483648000,15328051200, %U A282170 38320128000,199264665600,919683072000,4828336128000,11955879936000,71735279616000,334764638208000,1506440871936000,5021469573120000,30128817438720000 %N A282170 a(n) is the minimal product of a positive integer sequence of length n with no duplicate substrings (forward or backward) of length greater than 1, and no self-adjacent terms. %e A282170 a(1) = 1 via [1]; %e A282170 a(2) = 2 via [1,2]; %e A282170 a(3) = 6 via [1,2,3]; %e A282170 a(4) = 6 via [1,2,3,1]; %e A282170 a(5) = 24 via [1,2,3,1,4]; %e A282170 a(6) = 48 via [1,2,3,1,4,2]; %e A282170 a(7) = 120 via [1,2,3,1,4,5,1]; %e A282170 a(8) = 240 via [1,2,3,1,4,2,5,1]; %e A282170 a(9) = 1440 via [1,2,3,1,4,2,5,1,6]; %e A282170 a(10) = 2880 via [1,2,3,1,4,2,5,1,6,2]; %e A282170 a(11) = 10080 via [1,2,3,1,4,2,5,1,6,7,1]. %e A282170 Examples: %e A282170 [1,1] is invalid because 1 is self-adjacent. %e A282170 [1,2,3,1,2] is invalid because the substring [1,2] appears twice. %e A282170 [1,2,1] is invalid because the substring [1,2] appears twice (once forward and once backward). %Y A282170 Cf. A081456, A282164, A282169, A282170, A282193. %Y A282170 Cf. A282167 is the sum analog. %K A282170 nonn %O A282170 1,2 %A A282170 _Peter Kagey_, Feb 07 2017 %E A282170 Terms a(12) onward from _Max Alekseyev_, Feb 04 2025