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A026393 a(n) = T(n,n-2), where T is the array in A026386. 1
1, 4, 8, 17, 24, 39, 49, 70, 83, 110, 126, 159, 178, 217, 239, 284, 309, 360, 388, 445, 476, 539, 573, 642, 679, 754, 794, 875, 918, 1005, 1051, 1144, 1193, 1292, 1344, 1449, 1504, 1615, 1673, 1790, 1851, 1974, 2038, 2167, 2234, 2369, 2439, 2580, 2653, 2800 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Colin Barker, Table of n, a(n) for n = 2..1000

Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

FORMULA

G.f.: x^2*(1+3*x+2*x^2+3*x^3) / ((1-x)^3*(1+x)^2). - Emeric Deutsch, Feb 18 2004

From Colin Barker, Jan 26 2016: (Start)

a(n) = (18*n^2-46*n+(-1)^n*(13-6*n)+35)/16.

a(n) = (9*n^2-26*n+24)/8 for n even.

a(n) = (9*n^2-20*n+11)/8 for n odd.

(End)

PROG

(PARI) Vec(x^2*(1+3*x+2*x^2+3*x^3)/((1-x)^3*(1+x)^2) + O(x^100)) \\ Colin Barker, Jan 26 2016

CROSSREFS

Sequence in context: A151911 A037242 A158139 * A298950 A213494 A092321

Adjacent sequences:  A026390 A026391 A026392 * A026394 A026395 A026396

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified February 20 01:26 EST 2018. Contains 299357 sequences. (Running on oeis4.)