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 A158880 #18 Feb 16 2025 08:33:10 %S A158880 6,8100,7741440,7138643400,6551815840350,6009209192448000, %T A158880 5511006731579419434,5054037303588059379600,4634949992739663836897280, %U A158880 4250612670512943969574312500,3898145031429828405122837863554 %N A158880 Number of spanning trees in C_6 X P_n. %C A158880 A linear divisibility sequence of order 18. - _Peter Bala_, May 02 2014 %H A158880 Alois P. Heinz, <a href="/A158880/b158880.txt">Table of n, a(n) for n = 1..100</a> %H A158880 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CycleGraph.html">Cycle Graph</a> %H A158880 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PathGraph.html">Path Graph</a> %H A158880 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SpanningTree.html">Spanning Tree</a> %H A158880 <a href="/index/Di#divseq">Index to divisibility sequences</a> %F A158880 See program. %F A158880 a(n) = 6*U(n-1,3/2)^2*U(n-1,5/2)^2*U(n-1,3) = 6*A001906(n)^2*A004254(n)^2*A001109(n), where U(n,x) is a Chebyshev polynomial of the second kind. - _Peter Bala_, May 02 2014 %p A158880 a:= n-> 6* (Matrix(1,18, (i,j)-> -sign(j-10) *[0, 1, 1350, 1290240, 1189773900, 1091969306725, 1001534865408000, 918501121929903239, 842339550598009896600, 772491665456610639482880][1+abs(j-10)]). Matrix(18, (i,j)-> if i=j-1 then 1 elif j=1 then [842608511100, -639641521152, 276457068288, -65829977967, 8292106368, -524839680, 16393554, -232704, 1152, -1][1+abs(i-9)] else 0 fi)^n) [1,10]: seq(a(n), n=1..15); %Y A158880 Column 6 of A173958. %Y A158880 Cf. A001353, A003690, A003753, A003733, A158898. A001109, A001906, A004254. %K A158880 nonn,easy %O A158880 1,1 %A A158880 _Alois P. Heinz_, Mar 28 2009