A169636 Number of permutations of A004001 sequence vectors:a(n)=Length[Permutations[Table[A004001[i], {i, 0, m}]]].

1, 2, 3, 12, 30, 180, 1260, 5040, 15120, 151200, 1663200

Offset: 0

Author

Roger L. Bagula, Apr 04 2010

Keywords

• nonn
• uned

Programs

Mathematica

(*A004001*)
f[0] = 0; f[1] = 1; f[2] = 1;
f[n_] := f[n] = f[f[n - 1]] + f[n - f[n - 1]];
a[m_] := Length[Permutations[Table[f[i], {i, 0, m}]]];
b = Table[a[m], {m, 0, 10}]

Formula

f(n) = f(f(n - 1)) + f(n - f(n - 1));

a(n)=Length[Permutations[Table[f(i), {i, 0, m}]]]