A098971 a(0)=1; for n > 0, a(n)=a(floor(n/2))+2*a(floor(n/4)).

1, 3, 5, 5, 11, 11, 11, 11, 21, 21, 21, 21, 21, 21, 21, 21, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 171, 171, 171, 171, 171

Offset

0,2

Links

Table of n, a(n) for n=0..68.

Formula

n>0, a(n) = (1/3)*(8*2^(floor(log(n)/log(2)))+(-1)^(floor(log(n)/log(2)))).

Prog

(PARI) a(n)=if(n<1, 1, (1/3)*(8*2^(floor(log(n)/log(2)))+(-1)^(floor(log(n)/log(2)))))
(Python)
def A098971(n): return ((1<<(m:=n.bit_length()+2))+(1 if m&1 else -1))//3 # Chai Wah Wu, Oct 10 2024

Crossrefs

a(2^n) gives the Jacobsthal sequence A001045(n+3).

Cf. A001045, A007731.

Sequence in context: A190864 A155537 A164663 * A093572 A317650 A240731

Adjacent sequences: A098968 A098969 A098970 * A098972 A098973 A098974

Keyword

nonn,changed

Author

Benoit Cloitre, Oct 23 2004

Status

approved