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A168566 (n-1)*(n+2)*(n^2+n+2)/4. 1
0, 8, 35, 99, 224, 440, 783, 1295, 2024, 3024, 4355, 6083, 8280, 11024, 14399, 18495, 23408, 29240, 36099, 44099, 53360, 64008, 76175, 89999, 105624, 123200, 142883, 164835, 189224, 216224, 246015, 278783, 314720, 354024, 396899, 443555, 494208 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The products of two consecutive numbers in this sequence may be evaluated in terms of the Frobenius numbers for 5 consecutive integers, A138985(n) = F(n): for n>0, a(2n-1)*a(2n) = F(4n^2-2)^2 - (2n)^2; a(2n)*a(2n+1) = F(4n^2+4n)^2 - (2n+1)^2. - Charlie Marion, Jan 23 2012

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Index to sequences with linear recurrences with constant coefficients, signature (5,-10,10,-5,1).

FORMULA

G.f.: x^2*(-8+5*x-4*x^2+x^3)/(x-1)^5. - R. J. Mathar, Jan 04 2011

a(n) = A000217(n)^2-1. - Charlie Marion, Sep 27 2011

MATHEMATICA

s=0; lst={s}; Do[s+=n^3; AppendTo[lst, s], {n, 2, 5!}]; lst [From Vladimir Joseph Stephan Orlovsky, Apr 27 2010]

PROG

(MAGMA) [(n-1)*(n+2)*(n^2+n+2)/4: n in [1..50]]

CROSSREFS

Cf. A000578 (first differences).

Sequence in context: A136016 A100907 A212903 * A058102 A212674 A189592

Adjacent sequences:  A168563 A168564 A168565 * A168567 A168568 A168569

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 30 2009

STATUS

approved

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Last modified November 26 01:29 EST 2014. Contains 250017 sequences.