OFFSET
0,3
COMMENTS
Next term is too large to include.
Odd terms are the product of previous terms and even terms are the sum of previous terms.
LINKS
Iain Fox, Table of n, a(n) for n = 0..18
Iain Fox, Table of n, a(n) for n = 0..32
FORMULA
a(n) = a(n-1) + 2*a(n-2), for even n > 2.
a(n) = a(n-1) * a(n-2)^2, for odd n > 1.
EXAMPLE
5 is odd, so a(5) = 1 * 1 * 2 * 2 * 6 = 24.
6 is even, so a(6) = 1 + 1 + 2 + 2 + 6 + 24 = 36.
MATHEMATICA
a[0]:= 1; a[n_]:= If[OddQ[n], Product[a[j], {j, 0, n-1}], Sum[a[j], {j, 0, n -1}]]; Table[a[n], {n, 0, 15}] (* G. C. Greubel, Oct 19 2018 *)
PROG
(PARI) first(n) = my(res = vector(n, i, 1)); for(x=3, n, res[x]=if(x%2, sum(i=1, x-1, res[i]), prod(i=1, x-1, res[i]))); res
(PARI) first(n) = my(res = vector(n, i, 1)); res[3]++; for(x=4, n, res[x]=if(x%2, res[x-1]+2*res[x-2], res[x-1]*res[x-2]^2)); res
CROSSREFS
KEYWORD
nonn
AUTHOR
Iain Fox, Oct 17 2018
STATUS
approved