%I A107873
%S A107873 1,4,1,15,5,1,84,28,6,1,715,220,45,7,1,8568,2380,455,66,8,1,134596,
%T A107873 33649,5985,816,91,9,1,2629575,593775,98280,12650,1330,120,10,1,
%U A107873 61523748,12620256,1947792,237336,23751,2024,153,11,1,1677106640
%N A107873 Triangle, read by rows, where T(n,k) = C(n*(n-1)/2-k*(k-1)/2+n-k+3, n-k).
%C A107873 Remarkably, the following matrix products are all equal to A107876: A107862^-1*A107867 
               = A107867^-1*A107870 = A107870^-1*A107873.
%e A107873 Triangle begins:
%e A107873 1;
%e A107873 4,1;
%e A107873 15,5,1;
%e A107873 84,28,6,1;
%e A107873 715,220,45,7,1;
%e A107873 8568,2380,455,66,8,1;
%e A107873 134596,33649,5985,816,91,9,1;
%e A107873 2629575,593775,98280,12650,1330,120,10,1; ...
%o A107873 (PARI) T(n,k)=binomial(n*(n-1)/2-k*(k-1)/2 +n-k+3,n-k)
%Y A107873 Cf. A107862, A107865, A107867, A107876, A107870, A107874, A107875.
%Y A107873 Sequence in context: A145829 A016115 A164794 this_sequence A156290 A080419 
               A095307
%Y A107873 Adjacent sequences: A107870 A107871 A107872 this_sequence A107874 A107875 
               A107876
%K A107873 nonn,tabl
%O A107873 0,2
%A A107873 Paul D. Hanna (pauldhanna(AT)juno.com), Jun 04 2005