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A064763 a(n) = 28*n^2. 3
0, 28, 112, 252, 448, 700, 1008, 1372, 1792, 2268, 2800, 3388, 4032, 4732, 5488, 6300, 7168, 8092, 9072, 10108, 11200, 12348, 13552, 14812, 16128, 17500, 18928, 20412, 21952, 23548, 25200, 26908, 28672, 30492, 32368, 34300, 36288, 38332 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of edges in a complete 8-partite graph of order 8n, K_n,n,n,n,n,n,n,n.

Sequence found by reading the line from 0, in the direction 0, 28,..., in the square spiral whose vertices are the generalized 16-gonal numbers. - Omar E. Pol, Jul 03 2014

LINKS

Table of n, a(n) for n=0..37.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = 56*n+a(n-1)-28 (with a(0)=0). - Vincenzo Librandi, Aug 07 2010

a(n) = 28*A000290(n) = 14*A001105(n) = 7*A016742(n) = 4*A033582(n) = 2*A144555(n). - Omar E. Pol, Jul 03 2014

G.f.: 28*x*(1+x)/(1-x)^3. - Vincenzo Librandi, Mar 30 2015

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Vincenzo Librandi, Mar 30 2015

a(n) = t(8*n) - 8*t(n), where t(i) = i*(i+k)/2 for any k. Special case (k=1): a(n) = A000217(8*n) - 8*A000217(n). - Bruno Berselli, Aug 31 2017

MATHEMATICA

CoefficientList[Series[28 x (1 + x) / (1 - x)^3, {x, 0, 40}], x] (* Vincenzo Librandi, Mar 30 2015 *)

PROG

(MAGMA) [28*n^2: n in [0..40]] /* or */ I:=[0, 28, 112]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..40]]; // Vincenzo Librandi, Mar 30 2015

(PARI) a(n)=28*n^2 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

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

Similar sequences are listed in A244630.

Sequence in context: A118613 A245153 A295981 * A219594 A042534 A042536

Adjacent sequences:  A064760 A064761 A064762 * A064764 A064765 A064766

KEYWORD

nonn,easy

AUTHOR

Roberto E. Martinez II, Oct 18 2001

STATUS

approved

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Last modified October 21 11:42 EDT 2019. Contains 328296 sequences. (Running on oeis4.)