OFFSET
0,2
LINKS
W. Mlotkowski, A. Romanowicz, A family of sequences of binomial type, Probability and Mathematical Statistics, Vol. 33, Fasc. 2 (2013), pp. 401-408.
FORMULA
a(n) = 2*A043301(n-1) = 2^n*Sum_{k=0..n-1}(n+k-1)!/(n-k-1)!/k!/4^k for n>0, with a(0) = 1.
PROG
(PARI) a(n)=if(n==0, 1, 2^n*sum(k=0, n-1, (n+k-1)!/(n-k-1)!/k!/4^k))
(PARI) a(n)=local(X=x+x*O(x^n), Y=y+y*O(y^n)); sum(k=0, n, abs((matrix(n+1, n+1, m, j, if(m>=j, (m-1)!*polcoeff(polcoeff(exp(X+Y*X^2/2+X*Y), m-1, x), j-1, y)))^-1)[n+1, k+1]))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 21 2005
STATUS
approved