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A071252 a(n) = n*(n - 1)*(n^2 + 1)/2. 1
0, 0, 5, 30, 102, 260, 555, 1050, 1820, 2952, 4545, 6710, 9570, 13260, 17927, 23730, 30840, 39440, 49725, 61902, 76190, 92820, 112035, 134090, 159252, 187800, 220025, 256230, 296730, 341852, 391935, 447330, 508400, 575520, 649077, 729470, 817110, 912420 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

T. A. Gulliver, Sequences from Arrays of Integers, Int. Math. Journal, Vol. 1, No. 4, pp. 323-332, 2002.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..2000

FORMULA

a(n) = floor(n^5/(n+1))/2. - Gary Detlefs, Mar 31 2011

a(n) = 5*a(n-1)-10*a(n-2)+10*a(n-3)-5*a(n-4)+a(n-5) n>4, a(0)=0, a(1)=0, a(2)=5, a(3)=30, a(4)=102. - Yosu Yurramendi, Sep 03 2013

G.f.:  x^2*(5+5*x+2*x^2)/(1-x)^5. - Joerg Arndt, Sep 04 2013

From Indranil Ghosh, Apr 05 2017: (Start)

a(n) = A002378(n) * A002522(n) / 2.

E.g.f.: exp(x)*x^2*(5 + 5x + x^2)/2.

(End)

MATHEMATICA

f[n_] := n (n - 1) (n^2 + 1)/2 (* Or *) f[n_] := Floor[n^5/(n + 1)]/2; Array[f, 38, 0] (* Robert G. Wilson v, Apr 01 2012 *)

PROG

(MAGMA) [n*(n-1)*(n^2+1)/2: n in [0..40]]; // Vincenzo Librandi, Jun 14 2011

(PARI) a(n)=n*(n-1)*(n^2+1)/2; \\ Joerg Arndt, Sep 04 2013

(Python) def a(n): return  n*(n - 1)*(n**2 + 1)/2 # Indranil Ghosh, Apr 05 2017

CROSSREFS

Cf. A002378, A002522.

Sequence in context: A128302 A258582 A288679 * A174002 A030506 A062990

Adjacent sequences:  A071249 A071250 A071251 * A071253 A071254 A071255

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jun 12 2002

STATUS

approved

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Last modified October 16 16:18 EDT 2019. Contains 328101 sequences. (Running on oeis4.)