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 A288959 a(n) = n^2*(n^2 - 1)^2/2. 0
 0, 18, 288, 1800, 7200, 22050, 56448, 127008, 259200, 490050, 871200, 1472328, 2384928, 3726450, 5644800, 8323200, 11985408, 16901298, 23392800, 31840200, 42688800, 56455938, 73738368, 95220000, 121680000, 154001250, 193179168, 240330888, 296704800, 363690450 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Except for n = 2, gives the detour index of the n X n rook and rook complement graph. Also the detour index of the n X n king and n X n queen graphs. - Eric W. Weisstein, Dec 16 2017 LINKS Eric Weisstein's World of Mathematics, Detour Index Eric Weisstein's World of Mathematics, King Graph Eric Weisstein's World of Mathematics, Queen Graph Eric Weisstein's World of Mathematics, Rook Complement Graph Eric Weisstein's World of Mathematics, Rook Graph Index entries for linear recurrences with constant coefficients, signature (7, -21, 35, -35, 21, -7, 1). FORMULA a(n) = n^2*(n^2 - 1)^2/2. a(n) = 7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)-7*a(n-6)+a(n-7). G.f.: (-18*x^2*(1+x)*(1+8*x+x^2))/(-1+x)^7. a(n) = 18 *A001249(n-2). - R. J. Mathar, Dec 17 2017 MATHEMATICA Table[n^2 (n^2 - 1)^2/2, {n, 20}] LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {0, 18, 288, 1800, 7200, 22050, 56448}, 20] CoefficientList[Series[-((18 x (1 + x) (1 + 8 x + x^2))/(-1 + x)^7), {x, 0, 20}], x] 18 Binomial[Range[0, 20] + 2, 3]^2 (* Eric W. Weisstein, Dec 20 2017 *) PROG (PARI) a(n) = n^2*(n^2-1)^2/2; \\ Altug Alkan, Dec 20 2017 CROSSREFS Sequence in context: A245924 A035119 A230235 * A294327 A286725 A226998 Adjacent sequences:  A288956 A288957 A288958 * A288960 A288961 A288962 KEYWORD nonn,easy AUTHOR Eric W. Weisstein, Jun 20 2017 STATUS approved

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Last modified January 17 09:54 EST 2020. Contains 330949 sequences. (Running on oeis4.)