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A026041 a(n) = d(n)/2, where d = A026040. 1
12, 20, 32, 49, 72, 102, 140, 187, 244, 312, 392, 485, 592, 714, 852, 1007, 1180, 1372, 1584, 1817, 2072, 2350, 2652, 2979, 3332, 3712, 4120, 4557, 5024, 5522, 6052, 6615, 7212, 7844, 8512, 9217, 9960, 10742, 11564, 12427, 13332, 14280, 15272, 16309, 17392, 18522, 19700, 20927, 22204, 23532, 24912, 26345 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 4..1000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

FORMULA

For n>4, a(n) = a(n-1)+A022856(n+2). - Levi R. Self (levi.r.self(AT)gmail.com), Aug 04 2007

G.f.: -x^4*(7*x^3-24*x^2+28*x-12)/(x-1)^4. - Colin Barker, Oct 07 2012

For n>3, a(n) = n*(n^2-3*n+14)/6. - Vincenzo Librandi, Oct 17 2013

MATHEMATICA

CoefficientList[Series[-(7 x^3 - 24 x^2 + 28 x - 12)/(x - 1)^4, {x, 0, 60}], x] (* Vincenzo Librandi, Oct 17 2013 *)

PROG

(MAGMA) [n*(n^2-3*n+14)/6: n in [4..60]]; // Vincenzo Librandi, Oct 17 2013

CROSSREFS

Sequence in context: A334418 A269453 A082800 * A299028 A082296 A187766

Adjacent sequences:  A026038 A026039 A026040 * A026042 A026043 A026044

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified August 8 19:29 EDT 2020. Contains 336298 sequences. (Running on oeis4.)