OFFSET
0,2
FORMULA
G.f.: 1 + x * (Sum_{n>=0} prime(a(n)) * x^n)^2.
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Sum[Prime[a[k]] Prime[a[n - k - 1]], {k, 0, n - 1}]; Table[a[n], {n, 0, 9}]
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Ilya Gutkovskiy, Nov 10 2020
EXTENSIONS
a(10)-a(11) from Daniel Suteu, Nov 10 2020
a(12) from Jinyuan Wang, Nov 14 2020
STATUS
approved