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A024875 a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = floor( n/2 ), s = natural numbers >= 3. 1
12, 15, 38, 45, 82, 94, 148, 166, 240, 265, 362, 395, 518, 560, 712, 764, 948, 1011, 1230, 1305, 1562, 1650, 1948, 2050, 2392, 2509, 2898, 3031, 3470, 3620, 4112, 4280, 4828, 5015, 5622, 5829, 6498, 6726, 7460, 7710, 8512, 8785, 9658, 9955, 10902, 11224, 12248, 12596 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 2..1000

Index entries for linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1)

FORMULA

G.f.: x^2*(12+3*x-13*x^2-2*x^3+4*x^4) / ((1+x)^3*(x-1)^4). - R. J. Mathar, Sep 25 2013

a(n) = 12*A058187(n-2) +3*A058187(n-3) -13*A058187(n-4) -2*A058187(n-5) +4*A058187(n-6). - R. J. Mathar, Sep 25 2013

From Colin Barker, Jan 29 2016: (Start)

a(n) = (4*n^3+3*((-1)^n+19)*n^2+2*(15*(-1)^n+61)*n+75*((-1)^n-1))/48.

a(n) = (2*n^3+30*n^2+76*n)/24 for n even.

a(n) = (2*n^3+27*n^2+46*n-75)/24 for n odd. (End)

MATHEMATICA

CoefficientList[Series[(12 + 3 x - 13 x^2 - 2 x^3 + 4 x^4)/((1 + x)^3 (x - 1)^4), {x, 0, 50}], x] (* Vincenzo Librandi, Sep 25 2013 *)

LinearRecurrence[{1, 3, -3, -3, 3, 1, -1}, {12, 15, 38, 45, 82, 94, 148}, 50] (* Harvey P. Dale, Jul 21 2015 *)

PROG

(PARI) Vec(x^2*(12+3*x-13*x^2-2*x^3+4*x^4)/((1+x)^3*(x-1)^4) + O(x^100)) \\ Colin Barker, Jan 29 2016

CROSSREFS

Sequence in context: A277082 A087098 A109315 * A152190 A079322 A167304

Adjacent sequences:  A024872 A024873 A024874 * A024876 A024877 A024878

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified February 25 03:32 EST 2018. Contains 299630 sequences. (Running on oeis4.)