A107872 - OEIS

%I #12 Sep 08 2022 08:45:19

%S 1,4,21,165,1820,26334,475020,10295472,260932815,7575968400,

%T 247994680648,9036996468045,362827605867363,15913388077274800,

%U 757000487505568680,38819452599736372800,2134712294190092847615

%N Column 1 of triangle A107870; a(n) = C(n*(n+1)/2 + n+2, n).

%H Vincenzo Librandi, <a href="/A107872/b107872.txt">Table of n, a(n) for n = 0..200</a>

%p A107872:=n->binomial(n*(n+1)/2+n+2,n): seq(A107872(n), n=0..20); # _Wesley Ivan Hurt_, Aug 09 2014

%t Table[Binomial[(n(n+1))/2+n+2,n],{n,0,20}] (* _Harvey P. Dale_, Aug 09 2014 *)

%o (PARI) a(n)=binomial(n*(n+1)/2+n+2,n)

%o (Magma) [Binomial((n^2+3*n+4) div 2,n): n in [0..20]] // _Vincenzo Librandi_, Aug 09 2014

%Y Cf. A107870, A107871.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jun 04 2005