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A064761 a(n) = 15 * n^2. 6
0, 15, 60, 135, 240, 375, 540, 735, 960, 1215, 1500, 1815, 2160, 2535, 2940, 3375, 3840, 4335, 4860, 5415, 6000, 6615, 7260, 7935, 8640, 9375, 10140, 10935, 11760, 12615, 13500, 14415, 15360, 16335, 17340, 18375, 19440, 20535, 21660, 22815 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of edges in a complete 6-partite graph of order 6n, K_n,n,n,n,n,n.

LINKS

Table of n, a(n) for n=0..39.

FORMULA

a(n) = A000290(n)*15 = A033428(n)*5 = A033429(n)*3. [Omar E. Pol, Dec 13 2008]

a(n) = A008587(n)*A008585(n). [Reinhard Zumkeller, Apr 12 2010]

a(n) = a(n-1) + 30*n - 15 for n>0, a(0)=0. [Vincenzo Librandi, Dec 15 2010]

a(n) = A022272(n) + A022272(-n). [Bruno Berselli, Mar 31 2015]

MAPLE

seq(bell(4, j)*(j-2)^2, j = 2 .. 41) ; # Zerinvary Lajos, Nov 29 2007

CROSSREFS

Cf. A000217, A000290, A022272, A033428, A033581, A033583.

Cf. A033429. [From Omar E. Pol, Dec 13 2008]

Sequence in context: A022287 A223344 A206238 * A005945 A223337 A110755

Adjacent sequences:  A064758 A064759 A064760 * A064762 A064763 A064764

KEYWORD

nonn,easy

AUTHOR

Roberto E. Martinez II, Oct 18 2001

STATUS

approved

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Last modified March 28 19:06 EDT 2017. Contains 284246 sequences.