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%I #12 Mar 27 2018 09:44:09
%S 0,8,26,64,124,216,342,512,728,1000,1330,1728,2196,2744,3374,4096,
%T 4912,5832,6858,8000,9260,10648,12166,13824,15624,17576,19682,21952,
%U 24388,27000,29790,32768,35936,39304,42874,46656,50652,54872,59318,64000,68920,74088,79506,85184,91124
%N a(n) = n^3 - (n mod 2).
%C a(n) is the circumference of the n X n X n grid graph for n > 1.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GraphCircumference.html">Graph Circumference</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GridGraph.html">Grid Graph</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3, -2, -2, 3, -1).
%F a(n) = (2 n^3 + (-1)^n - 1)/2.
%F a(n) = 3*a(n-1) - 2*a(n-2) - 2*a(n-3) + 3*a(n-4) - a(n-5).
%F G.f.: 2*x^2*(4 + x + x^2)/((-1 + x)^4*(1 + x)).
%p seq(n^3-modp(n,2), n=1..50); # _Muniru A Asiru_, Mar 25 2018
%t Table[n^3 - Mod[n, 2], {n, 20}]
%t Table[(2 n^3 + (-1)^n - 1)/2, {n, 20}]
%t LinearRecurrence[{3, -2, -2, 3, -1}, {0, 8, 26, 64, 124}, 20]
%t CoefficientList[Series[2 x (4 + x + x^2)/((-1 + x)^4 (1 + x)), {x, 0, 20}], x]
%o (GAP) List([1..50],n->n^3- n mod 2); # _Muniru A Asiru_, Mar 25 2018
%o (PARI) a(n) = n^3 - (n%2); \\ _Altug Alkan_, Mar 25 2018
%Y Cf. A137932 (circumference of n X n grid graph).
%K nonn,easy
%O 1,2
%A _Eric W. Weisstein_, Mar 25 2018
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