OFFSET
0,6
FORMULA
a(n) = Sum_{j=1..floor(n/3)} Sum_{i=j..floor((n-j)/2)} sign(c(i) + c(j) + c(n-i-j)), where c is the prime characteristic (A010051).
MAPLE
b:= proc(n, i, t) option remember; series(
`if`(n=0, t, `if`(i<1, 0, expand(x*b(n-i, min(n-i, i),
`if`(isprime(i), 1, t)))+b(n, i-1, t))), x, 4)
end:
a:= n-> coeff(b(n$2, 0), x, 3):
seq(a(n), n=0..66); # Alois P. Heinz, Oct 24 2021
MATHEMATICA
Table[Length@Select[IntegerPartitions[k, {3}], Or@@PrimeQ@#&], {k, 0, 66}] (* Giorgos Kalogeropoulos, Oct 24 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Oct 24 2021
STATUS
approved