A285507 a(1) = a(2) = 1, a(3) = a(4) = 2; a(n) = a(a(n-2)-1) + a(n-a(n-3)-1) for n > 4.

1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 8, 8, 8, 8, 8, 8, 8, 9, 9, 11, 11, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 16, 16, 17, 17, 17, 17, 18, 18, 21, 21, 21, 20, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 24, 24, 24, 24, 24, 25, 25, 26, 26, 26, 26, 27, 27, 32, 32, 34, 30, 31, 29, 34, 33, 34, 34, 33, 33, 34, 34

Offset: 1

Author

Altug Alkan, Apr 20 2017

Keywords

• nonn
• look

Examples

			a(5) = 3 because a(5) = a(a(3)-1) + a(5-a(2)-1) = a(1) + a(3) = 3.
		

Links

• Altug Alkan, Table of n, a(n) for n = 1..10000
• Altug Alkan, Alternative scatterplot of A285507

Crossrefs

Cf. A005185, A055748, A284523.

Programs

Mathematica

a[1]=a[2]=1; a[3]=a[4]=2; a[n_] := a[n] = a[a[n-2]-1] + a[n-a[n-3]-1]; Array[a, 88] (* Giovanni Resta, Apr 21 2017 *)

PARI

a=vector(10000); a[1]=a[2]=1; a[3]=a[4]=2; for(n=5, #a, a[n]=a[a[n-2]-1]+a[n-a[n-3]-1]); va = vector(10000, n, a[n])