19897

Appears in sequences

• Smallest number that requires n iterations of the unitary totient function (A047994) to reach 1.at n=23A003271
• Number of unrooted triangulations with reflection symmetry of a pentagon with n internal nodes.at n=9A005506
• Fibonacci sequence beginning 1, 32.at n=15A022402
• (n - phi(n)) | sigma(n) for composite n not congruent to 2 (mod 4).at n=29A055164
• Number of fat trees on n labeled vertices.at n=5A055779
• Numbers k such that 3*2^k - 7 is prime.at n=33A059747
• Number of length n+4 0..6 arrays with every five consecutive terms having four times some element equal to the sum of the remaining four.at n=10A249654
• a(n) = (-1) * round(j((1 + sqrt(-n))/2)), where j is j-invariant.at n=9A302142
• Numerator of the expected fraction of guests without a napkin in Conway's napkin problem with n guests.at n=6A341232
• Number of integer partitions of n containing all divisors of all parts.at n=44A371178