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a(n) = binomial(n+9,9)*2^n.
11

%I #54 Sep 08 2022 08:45:34

%S 1,20,220,1760,11440,64064,320320,1464320,6223360,24893440,94595072,

%T 343982080,1203937280,4074864640,13388840960,42844291072,133888409600,

%U 409541017600,1228623052800,3621204787200,10501493882880,30004268236800

%N a(n) = binomial(n+9,9)*2^n.

%C Number of 9D hypercubes in an (n+9)-dimensional hypercube. - _Zerinvary Lajos_, Jan 29 2010; corrected by _Michel Marcus_, Jan 10 2015

%H Vincenzo Librandi, <a href="/A140354/b140354.txt">Table of n, a(n) for n = 0..400</a>

%H Milan Janjic and Boris Petkovic, <a href="http://arxiv.org/abs/1301.4550">A Counting Function</a>, arXiv:1301.4550 [math.CO], 2013.

%H <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (20,-180,960,-3360,8064,-13440,15360,-11520,5120,-1024).

%F a(n) = A038207(n+9,9).

%F G.f.: 1/(1-2*x)^10. - _Harvey P. Dale_, Jul 18 2011

%F a(0)=1, a(1)=20, a(2)=220, a(3)=1760, a(4)=11440, a(5)=64064, a(6)=320320, a(7)=1464320, a(8)=6223360, a(9)=24893440; for n>9, a(n) = 20*a(n-1) - 180*a(n-2) + 960*a(n-3) - 3360*a(n-4) + 8064*a(n-5) - 13440*a(n-6) + 15360*a(n-7) - 11520*a(n-8) + 5120*a(n-9) - 1024*a(n-10). - _Harvey P. Dale_, Jul 18 2011

%F a(n) = 2*a(n-1) + A140325(n-1). - _Ruskin Harding_, May 13 2013

%F a(n) = Sum_{i=9..n+9} binomial(i,9)*binomial(n+9,i). - _Bruno Berselli_, Mar 23 2018

%F From _Amiram Eldar_, Jan 07 2022: (Start)

%F Sum_{n>=0} 1/a(n) = 18*log(2) - 1599/140.

%F Sum_{n>=0} (-1)^n/a(n) = 118098*log(3/2) - 6703713/140. (End)

%e For n=6, a(6) = 1*5005 + 10*3003 + 55*1365 + 220*455 + 715*105 + 2002*15 + 5005*1 = 320320.

%p seq(binomial(n+9,9)*2^n,n=0..23);

%t Table[Binomial[n + 9, 9] 2^n, {n, 0, 20}] (* _Zerinvary Lajos_, Jan 29 2010 *)

%t CoefficientList[Series[1/(1-2x)^10,{x,0,30}],x] (* _Harvey P. Dale_, Jul 18 2011 *)

%o (Sage) [lucas_number2(n, 2, 0)*binomial(n,9)/512 for n in range(9, 31)] # _Zerinvary Lajos_, Mar 10 2009

%o (PARI) a(n)=binomial(n+9,9)<<n \\ _Charles R Greathouse IV_, Jul 18 2011

%o (Magma) [2^n*Binomial(n+9, 9): n in [0..30]]; // _Vincenzo Librandi_, Oct 14 2011

%Y Cf. A038207, A140325.

%K nonn,easy

%O 0,2

%A _Zerinvary Lajos_, Jun 23 2008