OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n-1} A022168(n-1,k) * a(k) for n>0, with a(0)=1.
EXAMPLE
The recurrence: a(n) = Sum_{k=0..n-1} A022168(n-1,k) * a(k)
is illustrated by:
a(2) = 1*(1) + 5*(1) + 1*(2) = 8;
a(3) = 1*(1) + 21*(1) + 21*(2) + 1*(8) = 72;
a(4) = 1*(1) + 85*(1) + 357*(2) + 85*(8) + 1*(72) = 1552.
Triangle A022168 begins:
1;
1, 1;
1, 5, 1;
1, 21, 21, 1;
1, 85, 357, 85, 1;
1, 341, 5797, 5797, 341, 1;
1, 1365, 93093, 376805, 93093, 1365, 1; ...
PROG
(PARI) /* q-Binomial coefficients: */ {C_q(n, k)=if(n<k || k<0, 0, if(n==0 || k==0, 1, prod(j=n-k+1, n, 1-q^j)/prod(j=1, k, 1-q^j)))} /* q-Bell numbers = eigensequence of q-binomial triangle: */ {B_q(n)=if(n==0, 1, sum(k=0, n-1, B_q(k)*C_q(n-1, k)))} /* Eigensequence at q=4: */ {a(n)=subst(B_q(n), q, 4)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 10 2006
STATUS
approved