OFFSET
1,1
FORMULA
a(n) +(-4*n+3)*a(n-1) +2*(n-1)*(2*n-3)*a(n-2)=0. - R. J. Mathar, Nov 23 2014
EXAMPLE
a(3) = 1*3*5 + 2*4*6 = 15 + 48 = 63.
MATHEMATICA
Table[n!!+(n+1)!!, {n, 1, 41, 2}] (* Harvey P. Dale, Jan 22 2019 *)
PROG
(Python)
o=e=1
for n in range(1, 99, 2):
o*=n
e*=n+1
print(str(e+o), end=', ')
(PARI) a(n)=prod(i=1, n, 2*i-1)+prod(i=1, n, 2*i) \\ Ralf Stephan, Nov 28 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Nov 27 2013
STATUS
approved