A222559 a(0) = 0. If n is odd, a(n) = a(n-1) * n, otherwise a(n) = a(n-1) + n.

0, 0, 2, 6, 10, 50, 56, 392, 400, 3600, 3610, 39710, 39722, 516386, 516400, 7746000, 7746016, 131682272, 131682290, 2501963510, 2501963530, 52541234130, 52541234152, 1208448385496, 1208448385520, 30211209638000, 30211209638026, 815702660226702, 815702660226730

Offset: 0

Author

Alex Ratushnyak, Feb 24 2013

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..808

Crossrefs

Cf. A077138, A047904, A047905.

Programs

Mathematica

last = 0; Table[If[OddQ[n], last = n * last, last = n + last], {n, 0, 40}] (* T. D. Noe, Mar 01 2013 *)
nxt[{n_,a_}]:={n+1,If[EvenQ[n],a(n+1),a+n+1]}; NestList[nxt,{0,0},30][[All,2]] (* Harvey P. Dale, May 14 2019 *)

Python

a=0
for n in range(1,33):
    print(a, end=',')
    if n&1:
        a *= n
    else:
        a += n