39182082047domain: NAppears in sequencesPrimes of the form 3*6^k - 1.at n=8A186104Primes of the form k*6^m - 1, where k is a Mersenne prime (A000668) and m >= 0.at n=15A186687a(n) = 3*6^n-1.at n=13A198796a(n) is the least prime of the form 2^j*3^k - 1, j > 0, k > 0, j + k = n. a(n) = 0 if no such prime exists.at n=25A337437