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 A272058 Start with all terms set to 0. Then add n to the next n+3 terms for n=0,1,2,... . 2
 0, 0, 1, 3, 6, 10, 14, 20, 25, 33, 39, 49, 56, 68, 76, 90, 99, 115, 125, 143, 154, 174, 186, 208, 221, 245, 259, 285, 300, 328, 344, 374, 391, 423, 441, 475, 494, 530, 550, 588, 609, 649, 671, 713, 736, 780, 804, 850, 875, 923, 949, 999, 1026, 1078, 1106 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1). FORMULA G.f.: x^2*(1 + 2*x + x^2 - x^4)/((1 - x)^3*(1 + x)^2). a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) - a(n-4) + a(n-5) for n > 6. a(n) = (6*n^2 + 6*n - 23 + (7 - 2*n)*(-1)^n)/16 for n > 1. a(n) = floor((n+3)/4) * floor((3*n-4)/2) + (floor((n-1)/2) mod 2) * floor((3*n-3)/4) for n > 1. For n > 1, a(2n) = A095794(n). - Jon E. Schoenfield, Feb 19 2022 EXAMPLE n | 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, ... __________________________________________ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... + 0, 0, 0 + 1, 1, 1, 1, + 2, 2, 2, 2, 2 + 3, 3, 3, 3, 3, 3 + 4, 4, 4, 4, 4, 4, 4 + 5, 5, 5, 5, 5, 5, 5, 5 + 6, 6, 6, 6, 6, 6, 6, 6, 6 + 7, 7, 7, 7, 7, 7, 7, 7, 7, 7 + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8 + 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 + ... __________________________________________ a(n)|0, 0, 1, 3, 6,10,14,20,25,33,39, ... MAPLE A272058:=n->(6*n^2+6*n-23+(7-2*n)*(-1)^n)/16: 0, 0, seq(A272058(n), n=2..100); MATHEMATICA CoefficientList[Series[x^2*(1 + 2 x + x^2 - x^4)/((1 - x)^3*(1 + x)^2), {x, 0, 50}], x] (* or *) LinearRecurrence[{1, 2, -2, -1, 1, 0, 0}, {0, 0, 1, 3, 6, 10, 14}, 60] PROG (Magma) [0, 0] cat [(6*n^2+6*n-23+(7-2*n)*(-1)^n)/16 : n in [2..100]]; CROSSREFS Cf. A095794, A258087. Sequence in context: A079552 A334454 A236758 * A244360 A183863 A140949 Adjacent sequences: A272055 A272056 A272057 * A272059 A272060 A272061 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Apr 19 2016 STATUS approved

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Last modified January 31 12:38 EST 2023. Contains 359971 sequences. (Running on oeis4.)