# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a370109
Showing 1-1 of 1

%I A370109 #5 Feb 10 2024 09:05:56
%S A370109 -21,-60,-45,144,675,1764,3675,6720,11259,17700,26499,38160,53235,
%T A370109 72324,96075,125184,160395,202500,252339,310800,378819,457380,547515,
%U A370109 650304,766875,898404,1046115,1211280,1395219,1599300,1824939,2073600,2346795,2646084,2973075
%N A370109 a(n) = n^2*(2*n^2-23).
%C A370109 For n > 5, also the number of chordless cycles (all of length 4) in the torus grid graph C_n square C_n.
%H A370109 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ChordlessCycle.html">Chordless Cycle</a>
%H A370109 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GraphComplement.html">Graph Complement</a>
%H A370109 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TorusGridGraph.html">Torus Grid Graph</a>
%H A370109 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A370109 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5).
%F A370109 G.f.: 3*(7-15*x-15*x^2+7*x^3)/(-1+x)^5.
%t A370109 Table[n^2 (2 n^2 - 23), {n, 20}]
%t A370109 LinearRecurrence[{5, -10, 10, -5, 1}, {-21, -60, -45, 144, 675}, 20]
%t A370109 CoefficientList[Series[3 (7 - 15 x - 15 x^2 + 7 x^3)/(-1 + x)^5, {x, 0, 20}], x]
%K A370109 sign,easy
%O A370109 1,1
%A A370109 _Eric W. Weisstein_, Feb 10 2024

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE