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%I #5 Oct 05 2019 10:42:46
%S 1,4,15,84,715,8568,134596,2629575,61523748,1677106640,52179482355,
%T 1823810410032,70724320184700,3012192716517082,139737927523546800,
%U 7012067478708989884,378371310857796292200,21843987843214746108900
%N Column 0 of triangle A107873; a(n) = C( n*(n-1)/2 + n+3, n).
%t Table[Binomial[(n(n-1))/2+n+3,n],{n,0,20}] (* _Harvey P. Dale_, Oct 05 2019 *)
%o (PARI) a(n)=binomial(n*(n-1)/2+n+3,n)
%Y Cf. A107873, A107875.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Jun 04 2005
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