A339310 a(n) = a(n-1-a(n-1)) + a(n-a(n-2)) for n>2; starting with a(1) = a(2) = 1.

1, 1, 2, 3, 3, 3, 5, 4, 6, 5, 6, 8, 8, 6, 9, 8, 8, 11, 11, 10, 10, 14, 12, 11, 16, 15, 12, 17, 14, 17, 16, 18, 14, 19, 19, 16, 21, 22, 19, 21, 25, 18, 22, 25, 23, 24, 25, 25, 23, 31, 28, 22, 33, 28, 29, 32, 28, 29, 30, 30, 33, 35, 29, 33, 32, 28, 41, 36, 35

Offset: 1

Author

Pablo Hueso Merino, Dec 02 2020

Keywords

• nonn

Comments

{a(n)} is the Pinn F 1,0(n) sequence (see link section).

Examples

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

Links

• K. Pinn, A Chaotic Cousin Of Conway's Recursive Sequence, arXiv:cond-mat/9808031 [cond-mat.stat-mech], 1998.

Crossrefs

Cf. A005185, A070867, A046699.

Programs

Mathematica

a[1] = a[2] = 1; a[n_] := a[n] = a[n - 1 - a[n - 1]] + a[n - a[n - 2]]; Table[ a[n], {n, 1, 40}]

PARI

lista(nn) = {my(va = vector(nn)); va[1] = 1; va[2] = 1; for (n=3, nn, va[n]=va[n-1-va[n-1]]+va[n-va[n-2]];); va;} \\ Michel Marcus, Dec 07 2020

Python

a=[1,1]
for n in range(100):
    i1=len(a)-1-a[len(a)-1]
    i2=len(a)-a[len(a)-2]
    if i1>=0 and i2>=0 :
        a.append(a[i1]+a[i2])
    else :
        print("Sequence dies. Contains ", n+2, " terms.")
        break
print(a)