178739domain: NAppears in sequencesNumbers k such that 27*2^k+1 is prime.at n=37A032363Numbers n such that 235*2^n-1 is prime.at n=17A050869G.f.: exp( Sum_{n>=0} [ Sum_{k=0..2*n} A027907(n,k)^2 * x^k ]* x^n/n ), where A027907 is the triangle of trinomial coefficients.at n=13A186236