54568

Appears in sequences

• a(1) = 1; for n>1, a(n) = smallest number that is not a sum or product of any subset of the numbers a(1) to a(n-1).at n=19A065026
• Numbers k such that k + phi(k) + phi(phi(k)) is a repdigit.at n=24A116027
• Number of n X 3 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 4 binary array having a sum of one, with rows and columns of the latter in lexicographically nondecreasing order.at n=9A227382
• Smallest b such that the k consecutive primes starting with prime(n) are all base-b Wieferich primes, i.e., satisfy b^(p-1) == 1 (mod p^2). Square array A(n, k), read by antidiagonals downwards.at n=16A286816
• Expansion of Product_{k>=1} 1/((1 - x^k)*(1 - x^(4*k))).at n=37A318027
• A(n, k) is the k-th number b > 1 such that b^(prime(n+i)-1) == 1 (mod prime(n+i)^2) for each i = 0..4, with k running over the positive integers; square array, read by antidiagonals, downwards.at n=2A319062
• a(n) is the smallest b > 1 such that prime(n), prime(n+1), prime(n+2), prime(n+3) and prime(n+4) are all base-b Wieferich primes.at n=1A344829
• Numbers k such that A353802(k) / sigma(sigma(k)) is an integer > 1, where A353802(n) = Product_{p^e||n} sigma(sigma(p^e)).at n=39A353807