A370648 Number of ways to choose a subset s of [n] and then for each element in s choose a different prime factor.

1, 1, 2, 4, 6, 12, 22, 44, 56, 76, 130, 260, 376, 752, 1248, 1948, 2224, 4448, 5808, 11616, 16016, 24000, 38416, 76832, 94656, 114736, 181992, 204024, 274056, 548112, 743856, 1487712, 1593696, 2292992, 3590880, 4881120, 5630592, 11261184, 17559072, 24987360

Offset: 0

Author

Alois P. Heinz, Feb 25 2024

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..140

Crossrefs

Cf. A000040, A370582.

Programs

Maple

b:= proc(n, s) option remember; uses numtheory; `if`(n=0, 1, b(n-1, s)+
      add(b(n-1, select(x-> x b(n, {}):
seq(a(n), n=0..42);

Formula

a(p) = 2 * a(p-1) for prime p.