A330772 a(n) = 1 for n<1; for n >= 0, a(n+1) = 2*a(n-a(n)).

2, 2, 2, 4, 2, 4, 4, 4, 8, 4, 8, 4, 8, 4, 8, 8, 8, 16, 4, 16, 8, 16, 8, 16, 8, 16, 8, 8, 32, 2, 16, 16, 16, 16, 32, 4, 32, 4, 32, 8, 32, 16, 32, 16, 16, 64, 2, 32, 16, 32, 32, 8, 32, 16, 8, 4, 16, 64, 2, 32, 16, 32, 4, 4, 64, 4, 64, 4, 8, 32, 8, 8, 8, 128

Offset

1,1

Comments

From the current term count back the same number of terms and double it to obtain the next term. Because a(n) can exceed n, negative indexes are also occasionally referenced.

Links

Table of n, a(n) for n=1..74.

Example

a(1) = 2*a(0-a(0)) = 2*a(-1) = 2.
a(2) = 2*a(1-a(1)) = 2*a(-1) = 2.
a(3) = 2*a(2-a(2)) = 2*a(0) = 2.
a(4) = 2*a(3-a(3)) = 2*a(1) = 4.

Prog

(Python)
a = [2]
for n in range(1000):
    if(a[n] > n):
        a.append(2)
    else:
        a.append(2*a[n-a[n]])

Crossrefs

Cf. A281130, A070867, A004001.

Sequence in context: A222959 A309441 A220498 * A105681 A368548 A240039

Adjacent sequences: A330769 A330770 A330771 * A330773 A330774 A330775

Keyword

nonn

Author

Rok Cestnik, Dec 30 2019

Status

approved