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 A153784 4 times heptagonal numbers: 2n(5n-3). 3
 0, 4, 28, 72, 136, 220, 324, 448, 592, 756, 940, 1144, 1368, 1612, 1876, 2160, 2464, 2788, 3132, 3496, 3880, 4284, 4708, 5152, 5616, 6100, 6604, 7128, 7672, 8236, 8820, 9424, 10048, 10692, 11356, 12040, 12744, 13468, 14212, 14976, 15760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the line from 0, in the direction 0, 4,..., in the square spiral whose vertices are the generalized heptagonal numbers A085787. - Omar E. Pol, Jul 18 2012 LINKS Ivan Panchenko, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 10n^2 - 6n = A000566(n)*4 = A135706(n)*2. a(n)=20*n+a(n-1)-16 (with a(0)=0) - Vincenzo Librandi, Aug 03 2010 a(n) = A087348(n) - 1, n >= 1. - Omar E. Pol, Jul 18 2012 a(0)=0, a(1)=4, a(2)=28, a(n)=3*a(n-1)-3*a(n-2)+a(n-3). - Harvey P. Dale, Mar 19 2015 MATHEMATICA s=0; lst={s}; Do[s+=n; AppendTo[lst, s], {n, 4, 6!, 20}]; lst (* Vladimir Joseph Stephan Orlovsky, Apr 02 2009 *) Table[2n(5n-3), {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 4, 28}, 50] (* Harvey P. Dale, Mar 19 2015 *) PROG (PARI) a(n)=2*n*(5*n-3) \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Cf. A000566, A135706, A152773, A152785. Sequence in context: A203280 A085024 A085001 * A030117 A005634 A183485 Adjacent sequences:  A153781 A153782 A153783 * A153785 A153786 A153787 KEYWORD easy,nonn AUTHOR Omar E. Pol, Jan 02 2009 STATUS approved

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Last modified December 11 23:44 EST 2019. Contains 329945 sequences. (Running on oeis4.)