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 A244866 Let G denote the 7-node, 12-edge graph formed from a hexagon with main diagonals drawn and a node at the center; a(n) = number of magic labelings of G with magic sum 2n. 1
 1, 18, 114, 438, 1263, 3024, 6356, 12132, 21501, 35926, 57222, 87594, 129675, 186564, 261864, 359720, 484857, 642618, 839002, 1080702, 1375143, 1730520, 2155836, 2660940, 3256565, 3954366, 4766958, 5707954, 6792003, 8034828, 9453264, 11065296, 12890097, 14948066, 17260866, 19851462, 22744159 (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 OFFSET 0,2 LINKS Colin Barker, Table of n, a(n) for n = 0..1000 R. P. Stanley, Examples of Magic Labelings, Unpublished Notes, 1973 [Cached copy, with permission] Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).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 + 12*x + 21*x^2 + 4*x^3) / (1 - x)^6. From Colin Barker, Jan 11 2017: (Start) a(n) = (n + 1)*(n + 2)*(19*n^3 + 63*n^2 + 68*n + 30) / 60. 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) MATHEMATICA LinearRecurrence[{6, -15, 20, -15, 6, -1}, {1, 18, 114, 438, 1263, 3024}, 40] (* Harvey P. Dale, Nov 09 2022 *) PROG (PARI) Vec((1 + 12*x + 21*x^2 + 4*x^3) / (1 - x)^6 + O(x^40)) \\ Colin Barker, Jan 11 2017 CROSSREFS Sequence in context: A160765 A192511 A324623 * A125328 A126486 A251937 Adjacent sequences: A244863 A244864 A244865 * A244867 A244868 A244869 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jul 07 2014 STATUS approved

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Last modified July 13 21:44 EDT 2024. Contains 374288 sequences. (Running on oeis4.)