A087836 a(n) = a(a(a(a(n-1)))) + a(n - a(n-1)) with a(1)=a(2)=1.

1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 15

Offset: 1

Author

Roger L. Bagula, Oct 07 2003

Keywords

• nonn

Links

• Joerg Arndt, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004001. Different from A087817.

Programs

Maple

a:= proc(n) option remember; `if`(n<3, 1,
      a(a(a(a(n-1)))) +a(n-a(n-1)))
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, Aug 06 2017

Mathematica

a[n_Integer?Positive] := a[n] =a[a[a[a[n-1]]]] + a[n - a[n-1]]; a[1] = a[2] = 1; Table[a[n], {n, 1, 256}]

PARI

lista(nn) = {va = vector(nn); va[1] = 1; va[2] = 1; for (n=3, nn, va[n] = va[va[va[va[n-1]]]]+va[n-va[n-1]];); va;} \\ Michel Marcus, Aug 06 2017

Extensions

Corrected by Michel Marcus, Aug 06 2017