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 A322039 Expansion of (1 + x)^2 / ((1 - x)^2*(1 + 2*x)^2). 2
 1, 0, 4, -4, 16, -28, 72, -148, 336, -716, 1560, -3332, 7136, -15164, 32168, -67956, 143216, -300972, 631096, -1320420, 2757376, -5747740, 11961544, -24855124, 51574416, -106877068, 221210712, -457334468, 944495136, -1948642556 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Connected with tiling of torus by squares (see A322038). LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (-2,3,4,-4). FORMULA From Colin Barker, Dec 04 2018: (Start) a(n) = -2*a(n-1) + 3*a(n-2) + 4*a(n-3) - 4*a(n-4) for n>3. a(n) = (16 + 11*(-2)^n + 3*(4+(-2)^n)*n) / 27. (End) MATHEMATICA LinearRecurrence[{-2, 3, 4, -4}, {1, 0, 4, -4}, 100] (* Amiram Eldar, Dec 04 2018 *) PROG (PARI) Vec((1 + x)^2 / ((1 - x)^2*(1 + 2*x)^2) + O(x^40)) \\ Colin Barker, Dec 04 2018 CROSSREFS Cf. A322038, A322040. Sequence in context: A092959 A330054 A183433 * A158101 A038234 A099462 Adjacent sequences:  A322036 A322037 A322038 * A322040 A322041 A322042 KEYWORD sign,easy AUTHOR N. J. A. Sloane, Dec 03 2018 STATUS approved

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Last modified September 17 06:16 EDT 2021. Contains 347478 sequences. (Running on oeis4.)