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 A244868 Number of symmetric 5 X 5 matrices of nonnegative integers with zeros on the main diagonal and every row and column adding to n. 2
 1, 22, 158, 654, 1980, 4906, 10577, 20588, 37059, 62710, 100936, 155882, 232518, 336714, 475315, 656216, 888437, 1182198, 1548994, 2001670, 2554496, 3223242, 4025253, 4979524, 6106775, 7429526, 8972172, 10761058, 12824554, 15193130, 17899431, 20978352, 24467113, 28405334, 32835110, 37801086 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Colin Barker, Table of n, a(n) for n = 0..1000 R. P. Stanley, Examples of Magic Labelings, Unpublished Notes, 1973 [Cached copy, with permission] Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1). FORMULA G.f.: (1 + 16*x + 41*x^2 + 16*x^3 + x^4) / (1 - x)^6. From Colin Barker, Jan 11 2017: (Start) a(n) = (24 + 94*n + 165*n^2 + 155*n^3 + 75*n^4 + 15*n^5) / 24. a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>5. (End) PROG (PARI) Vec((1 + 16*x + 41*x^2 + 16*x^3 + x^4) / (1 - x)^6 + O(x^40)) \\ Colin Barker, Jan 11 2017 CROSSREFS Even bisection of row n=5 of A333351. Cf. A053494. Sequence in context: A041934 A027943 A224257 * A223913 A189416 A224185 Adjacent sequences: A244865 A244866 A244867 * A244869 A244870 A244871 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jul 07 2014 STATUS approved

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Last modified July 13 04:46 EDT 2024. Contains 374267 sequences. (Running on oeis4.)