231425domain: NAppears in sequencesUltra-useful primes: smallest k such that 2^(2^n) - k is prime.at n=17A058220Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change 1,0 0,-1 1,2 or -1,1.at n=44A264584