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 A360201 Number of induced paths in the n-ladder graph P_2 X P_n. 2
 1, 8, 25, 58, 117, 218, 387, 666, 1123, 1868, 3079, 5044, 8229, 13388, 21741, 35262, 57145, 92558, 149863, 242590, 392631, 635408, 1028235, 1663848, 2692297, 4356368, 7048897, 11405506, 18454653, 29860418, 48315339, 78176034, 126491659, 204667988 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..1000 Eric Weisstein's World of Mathematics, Ladder Graph Index entries for linear recurrences with constant coefficients, signature (3,-2,-1,1) FORMULA a(n) = 3*a(n-1) - 2*a(n-2) - a(n-3) + a(n-4) for n > 4. G.f.: x*(1 + 5*x + 3*x^2)/((1 - x)^2*(1 - x - x^2)). MATHEMATICA LinearRecurrence[{3, -2, -1, 1}, {1, 8, 25, 58}, 40] (* Harvey P. Dale, Dec 28 2023 *) PROG (PARI) Vec((1 + 5*x + 3*x^2)/((1 - x)^2*(1 - x - x^2)) + O(x^40)) CROSSREFS Row 2 of A360199. Sequence in context: A143371 A131423 A270867 * A004640 A250321 A011924 Adjacent sequences: A360198 A360199 A360200 * A360202 A360203 A360204 KEYWORD nonn,easy AUTHOR Andrew Howroyd, Jan 29 2023 STATUS approved

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Last modified August 6 06:42 EDT 2024. Contains 374960 sequences. (Running on oeis4.)