A333132 a(n) = n for n <= 3; thereafter a(n) = 2^(a(n-1)-1) + a(n-1).

1, 2, 3, 7, 71, 1180591620717411303495

Offset: 1

Author

Ilya Gutkovskiy, Mar 08 2020

Keywords

• nonn

Comments

The next term is too large to include.

a(n) = number of compositions of a(1) + number of compositions of a(2) + ... + number of compositions of a(n-1) for n > 2.

Examples

			a(5) = 71, 71 in base 2 (reverse order of digits) = 1110001.
                                                    |||   |
                                                    123   7
		

Crossrefs

Cf. A004249, A007516, A011782, A014221, A034797, A103527.

Programs

Mathematica

a[n_] := a[n] = If[n <= 3, n, 2^(a[n - 1] - 1) + a[n - 1]]; Table[a[n], {n, 1, 6}]

Formula

a(n) = n for n <= 2; thereafter a(n) = Sum_{k=1..n-1} 2^(a(k)-1).