27557

Appears in sequences

• a(n) = 4*prime(n)^2+1.at n=22A060429
• n*10^4-1, n*10^4-3, n*10^4-7 and n*10^4-9 are all prime.at n=7A064978
• 30*a(n) is the gap between sexy prime triples in the n-th sexy prime triple triple whose initial term is 7.at n=16A090776
• a(n) = 81*n^2 - 90*n + 26.at n=19A154295
• Number of 3 X n arrays containing n copies of 0..3-1 with no element 1 greater than its west, southwest or northwest neighbor modulo 3 and the upper left element equal to 0.at n=9A267164
• Bases b where exactly nine primes p with p < b exist such that p is a base-b Wieferich prime.at n=2A325885
• Numbers b > 1 such that the smallest four primes, i.e., 2, 3, 5 and 7 are base-b Wieferich primes.at n=31A339533