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 A348154 #95 Jun 12 2022 08:15:54 %S A348154 1,3,11,100,1063,15686,271975,5509456,126604661,3256687324, %T A348154 92655915831,2888838414540,97940953019995,3587315304010374, %U A348154 141162897496953263,5939167862427259456,266046178356979847881,12641661811772879875640,635092155152649300232063,33633813271235206436451100 %N A348154 Number of inequivalent strip arrangements. %C A348154 Given n strips, each of length n squares (dimensions 1 X n), a(n) is the number of distinct shapes that can be created by setting the strips side by side while satisfying the condition that the shape must include at least one row of length L=n squares (row considered to be a direction measured perpendicular to the strips). Shapes differing only by a rotation are considered to be equivalent. %H A348154 Joseph Rozhenko, <a href="/A348154/a348154.jpg">Illustration of a(3) = 11</a> %F A348154 From _Jinyuan Wang_, Oct 08 2021: (Start) %F A348154 a(2*k+1) = ((2*k+1)^(2*k+1) - (2*k)^(2*k+1) + (2*k+1)^k) / 2. %F A348154 a(2*k) = ((2*k)^(2*k) - (2*k-1)^(2*k) + (2*k)^k + (2*k-1)^k) / 2. %F A348154 (End) %o A348154 (PARI) a(n) = (n^n - (n-1)^n + n^(n\2) + !(n%2)*(n-1)^(n\2))/2; \\ _Jinyuan Wang_, Oct 08 2021 %Y A348154 Cf. A045531 (when rotations are considered distinct). %K A348154 nonn %O A348154 1,2 %A A348154 _Joseph Rozhenko_, Oct 04 2021 %E A348154 More terms from _Jinyuan Wang_, Oct 08 2021