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 A318405 #20 Mar 16 2020 13:06:02 %S A318405 0,1,1,1,1,1,1,1,2,2,1,1,5,5,3,1,1,12,15,13,5,1,1,27,49,71,34,8,1,1, %T A318405 58,163,409,287,89,13,1,1,121,537,2315,2596,1237,233,21,1,1,248,1739, %U A318405 12709,23393,18321,5205,610,34,1,1,503,5537,67919,205894,268893,124177,22105,1597,55 %N A318405 Rectangular array R read by antidiagonals: R(n,k) = F(n+1)^k - k*F(n-1)*F(n)^(k-1), where F(n) = A000045(n), the n-th Fibonacci number; n >= 0, k >= 1. %C A318405 Row index n begins with 0, column index begins with 1. %C A318405 R(n,k) is the number of Markov equivalence classes whose skeleton is a spider graph with k legs, each of which contains n nodes of degree at most two. See Corollary 4.2 in the paper by A. Radhakrishnan et al. below. %H A318405 A. Radhakrishnan, L. Solus, and C. Uhler. <a href="https://arxiv.org/abs/1706.06091">Counting Markov equivalence classes for DAG models on trees</a>, arXiv:1706.06091 [math.CO], 2017; Discrete Applied Mathematics 244 (2018): 170-185. %e A318405 The rectangular array R(n,k) begins: %e A318405 n\k| 1 2 3 4 5 6 7 %e A318405 ---+------------------------------------------------------------- %e A318405 0 | 0 1 1 1 1 1 1 %e A318405 1 | 1 1 1 1 1 1 1 %e A318405 2 | 1 2 5 12 27 58 121 %e A318405 3 | 2 5 15 49 163 537 1739 %e A318405 4 | 3 13 71 409 2315 12709 67919 %e A318405 5 | 5 34 287 2596 23393 205894 1769027 %e A318405 6 | 8 89 1237 18321 268893 3843769 53573477 %e A318405 7 | 13 233 5205 124177 2941661 67944057 1530787237 %o A318405 (Sage) %o A318405 def R(n, k): %o A318405 return fibonacci(n+1)^k-k*fibonacci(n-1)*fibonacci(n)^(k-1) %Y A318405 Columns include A000045, A001519, A318376, A318404. %Y A318405 Cf. A007984. %K A318405 nonn,tabl,easy %O A318405 0,9 %A A318405 _Liam Solus_, Aug 26 2018