W. Lang, Nov 30 2007 a(n,k)=C(n,k) tabl head (triangle) for A134832 (nr. of circular permutations of {1,2,...,n} with exactly k successor pairs (i,i+1) ). Note that due to cyclicity also (n,1) is a successor pair. n\k 0 1 2 3 4 5 6 7 8 9 ... 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 2 0 0 1 0 0 0 0 0 0 0 3 1 0 0 1 0 0 0 0 0 0 4 1 4 0 0 1 0 0 0 0 0 5 8 5 10 0 0 1 0 0 0 0 6 36 48 15 20 0 0 1 0 0 0 7 229 252 168 35 35 0 0 1 0 0 8 1625 1832 1008 448 70 56 0 0 1 0 9 13208 14625 8244 3024 1008 126 84 0 0 1 . . . First (k=0) column: A000757= [1,0,0,1,1,8,36,229,1625,13208,120288,1214673,13469897,...], circular permutations without any successor pair. Row sums give (n-1)!= A000142(n-1), n>=1. Alternating row sums give: A134833 = [1,-1,1,0,-2,12,-16,144,368,4768,...]. Because C(n,k)=binomial(n,k)*C(n-k,0), k>=1, this is a Scheffer triangle of the Appell type: ((1-ln(1-x))/e^x,x). See the e.g.f. of the first column (k=0) sequence A000757. I.e. the e.g.f. for column nr. k is ((1-ln(1-x))/e^x)*(x^k)/k!, k>=0, hence a(n,k)=binomial(n,k)*a(n-k,0), n>=0. The a-sequence for Appel type Sheffer triangles has always (e.)g.f 1. The z-sequence for such triangles is always (1+1/g(x))/x if g is the e.g.f. of the first (k=0) column. ###################################### e.o.f. ########################################################