68641

Appears in sequences

• Number of subgroups of index n in free group of rank 3.at n=4A027837
• Numerators of continued fraction convergents to sqrt(739).at n=9A042422
• Array T(n,k) = number of subgroups of index k in free group of rank n, read by antidiagonals.at n=25A049290
• Composite and every divisor (except 1) contains the digit 8.at n=13A062678
• Number of ways to place zero or more nonadjacent 0,0 1,0 2,1 3,2 4,0 4,1 4,2 5,0 polyhexes in any orientation on a planar nXnXn triangular grid.at n=9A155426
• Heptagonal numbers (A000566) that are semiprimes (A001358).at n=26A259676
• The first of three consecutive heptagonal numbers the sum of which is equal to the sum of three consecutive primes.at n=6A298301
• Number of well-formed formulas of length n in a formal propositional language with one unitary operator, one binary operator, and one propositional variable.at n=33A308616