%I A007799
%S A007799 1,1,1,1,2,2,1,1,3,6,9,5,1,4,12,30,44,26,3,1,5,20,70,170,250,169,35,1,
%T A007799 6,30,135,460,1110,1689,1254,340,15,1,7,42,231,1015,3430,8379,13083,
%U A007799 10408,3409,315,1,8,56,364,1960,8540,28994,71512,114064,96116,36260
%N A007799 Triangle read by rows: Whitney numbers of second kind a(n,k), n >= 1, 
               k >= 0, for the star poset.
%D A007799 F. J. Portier and T. P. Vaughan, Whitney numbers of the second kind for 
               the star poset, Europ. J. Combin., 11 (1990), 277-288.
%D A007799 K. Qiu and S. G. Akl, On some properties of the star graph, VLSI Design, 
               Vol. 2, No. 4 (1995), 389-396.
%F A007799 a(n, 0)=1, a(n, 1)=n-1, a(n, 2)=(n-1)(n-2), a(n, k)=a(n-1, k)+(n-1)a(n-1, 
               k-1)-(n-2)a(n-2, k-1)+(n-2)a(n-2, k-3) for k >= 3.
%F A007799 a(n, 0) = 1, a(n, 1) = n - 1, a(n, 2) = (n-1)(n-2); a(n, i) = (n-1)a(n-1, 
               i-1) + sum_{j=1 ... n-2} j a(j, i-3). Let C(m, n) be the binomial 
               coefficient m choose n. For 0 <= i <= ceil(3(n-1)/2) and n >= 1 we 
               have sum_{k=0 ... i+1} (-1)^k C(i+1, k) a(n+i+1-k, i) = 0. For example, 
               for i=2, we have a(n+3, 2) - 3a(n+2, 2) + 3a(n+1, 2) - a(n, 2) = 
               0. - Ke Qiu (kqiu(AT)brocku.ca), Feb 06 2005
%e A007799 1; 1,1; 1,2,2,1; 1,3,6,9,5; 1,4,12,30,44,26,3; ...
%Y A007799 Sequence in context: A010048 A055870 A088459 this_sequence A122888 A092113 
               A045995
%Y A007799 Adjacent sequences: A007796 A007797 A007798 this_sequence A007800 A007801 
               A007802
%K A007799 nonn,tabf,easy,nice
%O A007799 1,5
%A A007799 Frederick J. Portier [ fportier(AT)msmary.edu ]
%E A007799 More terms from Larry Reeves (larryr(AT)acm.org), Mar 22 2000