105965domain: NAppears in sequencesG.f. satisfies: A(x) = x + 2*A(x)^2 + 3*A(x)*A(A(x))^2 + 4*A(x)*A(A(x))*A(A(A(x)))^2 +...at n=6A153304Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) with a(0)=3, a(1)=4, a(2)=5.at n=18A280308Semiprimes k such that k+2 and k+6 are primes and k+4 and k+8 are all semiprimes.at n=30A392186