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 A064761 a(n) = 15*n^2. 8

%I

%S 0,15,60,135,240,375,540,735,960,1215,1500,1815,2160,2535,2940,3375,

%T 3840,4335,4860,5415,6000,6615,7260,7935,8640,9375,10140,10935,11760,

%U 12615,13500,14415,15360,16335,17340,18375,19440,20535,21660,22815

%N a(n) = 15*n^2.

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

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).

%F a(n) = A000290(n)*15 = A033428(n)*5 = A033429(n)*3. - _Omar E. Pol_, Dec 13 2008

%F a(n) = A008587(n)*A008585(n). - _Reinhard Zumkeller_, Apr 12 2010

%F a(n) = a(n-1) + 30*n - 15 for n>0, a(0)=0. - _Vincenzo Librandi_, Dec 15 2010

%F a(n) = A022272(n) + A022272(-n). - _Bruno Berselli_, Mar 31 2015

%F a(n) = t(6*n) - 6*t(n), where t(i) = i*(i+k)/2 for any k. Special case (k=1): a(n) = A000217(6*n) - 6*A000217(n). - _Bruno Berselli_, Aug 31 2017

%p seq(bell(4, j)*(j-2)^2, j = 2 .. 41) ; # _Zerinvary Lajos_, Nov 29 2007

%o (PARI) a(n)=15*n^2 \\ _Charles R Greathouse IV_, Jun 17 2017

%Y Cf. A000217, A000290, A022272, A033428, A033581, A033583, A033429.

%K nonn,easy

%O 0,2

%A _Roberto E. Martinez II_, Oct 18 2001

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Last modified October 17 12:56 EDT 2019. Contains 328112 sequences. (Running on oeis4.)