A284523 a(1) = a(2) = 1, a(3) = 2; a(n) = a(a(n-1)-1) + a(n-a(n-3)-1) for n > 3.

1, 1, 2, 2, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 6, 8, 8, 8, 8, 8, 8, 8, 8, 9, 11, 13, 13, 13, 11, 13, 13, 13, 13, 13, 13, 13, 13, 14, 16, 19, 21, 19, 16, 14, 16, 17, 21, 21, 21, 21, 19, 21, 21, 21, 21, 21, 21, 21, 21, 22, 24, 27, 32, 29, 26, 24, 21, 29, 27, 34, 34, 27, 27, 29, 34, 34, 34, 29, 27, 29, 32

Offset: 1

Author

Altug Alkan and Robert Israel, Mar 28 2017

Keywords

• nonn
• look

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Altug Alkan, Plot for n=0..10^6

Crossrefs

Cf. A004001, A005185, A055748.

Programs

Maple

a:= proc(n) option remember;
procname(procname(n-1)-1) + procname(n-procname(n-3)-1)
end proc:
a(1):= 1: a(2):= 1: a(3):= 2:
map(a, [$1..100]);

Mathematica

a[1] = a[2] = 1; a[3] = 2; a[n_] := a[n] = a[a[n - 1] - 1] + a[n - a[n - 3] - 1]; Array[a, 81] (* Michael De Vlieger, Mar 28 2017 *)