A084566 a(0)=1, a(2n) = 2a(2n-1)+a(n), a(2n+1) = 2a(2n)+2a(n).

1, 4, 12, 32, 76, 176, 384, 832, 1740, 3632, 7440, 15232, 30848, 62464, 125760, 253184, 508108, 1019696, 2043024, 4093312, 8194064, 16403008, 32821248, 65672960, 131376768, 262815232, 525692928, 1051510784, 2103147328

Offset

0,2

Comments

a(n) ~ 2^(n+e) with e = 2.9701632052178...

Links

Table of n, a(n) for n=0..28.

Formula

G.f. prod(k>=0, (1+2x^2^k)/(1-2x^2^k)).

Prog

(PARI) a(n)=if(n<1, n<1, if(n%2==0, 2*a(n-1)+a(n/2), 2*a(n-1)+2*a((n-1)/2)))

Crossrefs

Cf. A018819.

Sequence in context: A138517 A001934 A004403 * A208903 A079769 A107035

Adjacent sequences: A084563 A084564 A084565 * A084567 A084568 A084569

Keyword

nonn,easy

Author

Ralf Stephan, Jun 28 2003

Status

approved