login
A227366
a(0)=1, a(n+1) = a(n) + a(n-1)*a(n-2) + a(n-3)*a(n-4)*a(n-5) + a(n-6)*a(n-7)*a(n-8)*a(n-9) + ... + ...*a(0).
4
1, 1, 2, 3, 6, 13, 33, 118, 584, 4714, 76206, 2879841, 364389490, 220150411628, 1049813737275512, 80222580570107370160, 231117086585854944888597249, 84218767584329653007205530276477742, 18540809099930664963747242025045529905738135516
OFFSET
0,3
EXAMPLE
a(1) = a(0) = 1
a(2) = a(1) + a(0) = 2
a(3) = a(2) + a(1)*a(0) = 3
a(4) = a(3) + a(2)*a(1) + a(0) = 3 + 2 + 1 = 6
a(5) = a(4) + a(3)*a(2) + a(1)*a(0) = 6 + 3*2 + 1 = 13
PROG
(Python)
a = [1]*99
for n in range(20):
sum = i = 0
k = 1
while i<=n:
product = 1
for x in range(k):
product *= a[n-i]
i += 1
if i>n: break
sum += product
k += 1
a[n+1] = sum
print(str(a[n]), end=', ')
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jul 08 2013
STATUS
approved