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A086755 Sum_{k=1..n} k(k+1)^2/2. 0
2, 20, 92, 292, 742, 1624, 3192, 5784, 9834, 15884, 24596, 36764, 53326, 75376, 104176, 141168, 187986, 246468, 318668, 406868, 513590, 641608, 793960, 973960, 1185210, 1431612, 1717380, 2047052, 2425502, 2857952, 3349984, 3907552 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..31.

Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

FORMULA

(n+1)(n+2)(n+3)(3n^2+12n+10)/30 = 2*A024166(n+1).

G.f. 2*(1+4*x+x^2) / (x-1)^6 . - R. J. Mathar, Sep 15 2012

EXAMPLE

a(3)=(1*2)^2/2+(2*3)^2/2+(3.4)^2/2=2+18+72=92

PROG

(PARI) for(i=1, 20, print1(", "sum(j=1, i, (j*(j+1))^2/2)))

CROSSREFS

Sequence in context: A069187 A328510 A033840 * A107483 A220856 A035599

Adjacent sequences:  A086752 A086753 A086754 * A086756 A086757 A086758

KEYWORD

nonn,easy

AUTHOR

Jon Perry, Jul 31 2003

EXTENSIONS

More terms from Jason Earls, Aug 01 2003

STATUS

approved

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Last modified December 7 20:18 EST 2019. Contains 329847 sequences. (Running on oeis4.)