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A298030
Partial sums of A298029.
2
1, 4, 10, 22, 40, 73, 112, 163, 220, 289, 364, 451, 544, 649, 760, 883, 1012, 1153, 1300, 1459, 1624, 1801, 1984, 2179, 2380, 2593, 2812, 3043, 3280, 3529, 3784, 4051, 4324, 4609, 4900, 5203, 5512, 5833, 6160, 6499, 6844, 7201, 7564, 7939, 8320, 8713, 9112, 9523, 9940, 10369, 10804, 11251, 11704
OFFSET
0,2
FORMULA
G.f.: -(3*x^7 - 9*x^5 - 3*x^4 - 4*x^3 - 2*x^2 - 2*x - 1)/((1 - x)^2*(1 - x^2)).
From Colin Barker, Jan 25 2018: (Start)
a(n) = (9*n^2 - 18*n + 8) / 2 for n>3 and even.
a(n) = (9*n^2 - 18*n + 11) / 2 for n>3 and odd.
a(n) = 2*a(n-1) - 2*a(n-3) + a(n-4) for n>5. (End)
E.g.f.: ((8 - 9*x + 9*x^2)*cosh(x) + (11 - 9*x + 9*x^2)*sinh(x) - 6 + 6*x + 6*x^2 + x^3)/2. - Stefano Spezia, Aug 19 2023
PROG
(PARI) Vec((1 + 2*x + 2*x^2 + 4*x^3 + 3*x^4 + 9*x^5 - 3*x^7) / ((1 - x)^3*(1 + x)) + O(x^50)) \\ Colin Barker, Jan 25 2018
CROSSREFS
Cf. A298029.
Sequence in context: A301243 A177736 A061777 * A155369 A155404 A155360
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jan 21 2018
STATUS
approved