17997

Appears in sequences

• Number of primitive (aperiodic) word structures of length n using a 5-ary alphabet.at n=8A056276
• Numbers n such that phi(2n+1) = sigma(n).at n=42A067229
• Lucky numbers for which both the sum of the digits and the product of the digits is also a lucky number.at n=39A118559
• Half the number of n X n symmetric binary matrices with each 1 adjacent to an even number of other 1's.at n=5A140963