OFFSET
0,4
FORMULA
T(n,k) = Sum_{j=0..k} C(k,j)*[T^2](n-k+j-1,j) for n>k>=0, with T(n,n)=1, for n>=0.
EXAMPLE
Triangle T begins:
1;
1, 1;
2, 2, 1;
6, 6, 4, 1;
26, 26, 18, 8, 1;
162, 162, 114, 54, 16, 1;
1454, 1454, 1030, 506, 162, 32, 1;
18854, 18854, 13394, 6666, 2274, 486, 64, 1;
354258, 354258, 251962, 126134, 43798, 10346, 1458, 128, 1; ...
Matrix square T^2 begins:
1;
2, 1;
6, 4, 1;
26, 20, 8, 1;
162, 136, 68, 16, 1;
1454, 1292, 732, 236, 32, 1;
18854, 17400, 10648, 4036, 836, 64, 1; ...
where the BINOMIAL transform of diagonal 2 of T^2:
BINOMIAL[6,20,68,236,836,3020,11108,41516,...]
equals: [6,26,114,506,2274,10346,47634,221786,...]
which is diagonal 3 of T.
Specific examples:
T(4,1) = [T^2](2,0) + [T^2](3,1) = 6 + 20 = 26;
T(4,2) = [T^2](1,0) + 2*[T^2](2,1) + [T^2](3,2) = 2 + 2*4 + 8 = 18;
T(5,2) = [T^2](2,0) + 2*[T^2](3,1) + [T^2](4,2) = 6 + 2*20 + 68 = 114;
T(5,3) = [T^2](1,0) + 3*[T^2](2,1) + 3*[T^2](3,2) + [T^2](4,3) = 2 + 3*4 + 3*8 + 16 = 54.
PROG
(PARI) T(n, k)=if(n<k || k<0, 0, if(n==k, 1, if(n==k+1, 2^k, if(k==1, T(n, 0), sum(j=0, k, binomial(k, j)*sum(i=0, n-k+j-1, T(n-k+j-1, i)*T(i, j)))))))
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Paul D. Hanna, Jul 01 2008
STATUS
approved