92020domain: NAppears in sequencesTriangle read by rows: T(n,k) is the coefficient A_k in the transformation Sum_{k=0..n} x^k = Sum_{k=0..n} A_k*(x+3*(-1)^k)^k.at n=15A249268Numbers k such that the concatenation of 2^k - 1 and 2^(k - 1) - 1 is prime.at n=29A301806