login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A078446 a(1)=a(2)=1; a(n)=a(n-2)/2 if a(n-2) is even, a(n)=a(n-1)+a(n-2) otherwise. 9
1, 1, 2, 3, 1, 4, 5, 2, 7, 1, 8, 9, 4, 13, 2, 15, 1, 16, 17, 8, 25, 4, 29, 2, 31, 1, 32, 33, 16, 49, 8, 57, 4, 61, 2, 63, 1, 64, 65, 32, 97, 16, 113, 8, 121, 4, 125, 2, 127, 1, 128, 129, 64, 193, 32, 225, 16, 241, 8, 249, 4, 253, 2, 255, 1, 256, 257, 128, 385, 64, 449, 32, 481, 16, 497 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
The following sequences all have the same parity: A004737, A006590, A027052, A071028, A071797, A078358, A078446. - Jeremy Gardiner, Mar 16 2003
LINKS
FORMULA
a(n^2)=2^n-1; a(n^2+1)=1; a(n^2+2)=2^n; a(n^2+3)=2^n+1; a(n^2+4)=2^(n-1); a(n^2+5)=3*2^n+1 ...; inequality : a(n)/2^sqrt(n) <2
Sum(k=1, n^2, a(k)) = 2*(n-2)*2^n + n*(n+1)/2 + 4
MAPLE
a:= proc(n) option remember;
if n < 3 then 1
elif `mod`(procname(n-2), 2) = 0 then procname(n-2)/2
else procname(n-1) + procname(n-2)
fi
end:
seq(a(n), n=1..80); # G. C. Greubel, Nov 07 2019
MATHEMATICA
a[n_]:= a[n]= If[n<3, 1, If[EvenQ[a[n-2]], a[n-2]/2, a[n-1]+a[n-2]]];
Table[a[n], {n, 80}] (* G. C. Greubel, Nov 07 2019 *)
PROG
(PARI) a(n) = if(n<3, 1, if(a(n-2)%2==0, a(n-2)/2, a(n-1) + a(n-2) )); \\ G. C. Greubel, Nov 07 2019
(Sage)
@CachedFunction
def a(n):
if (n<3): return 1
elif (a(n-2)%2==0): return a(n-2)/2
else: return a(n-1) + a(n-2)
[a(n) for n in (1..80)] # G. C. Greubel, Nov 07 2019
CROSSREFS
Sequence in context: A328456 A253887 A026370 * A357241 A055447 A055448
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Dec 31 2002
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 3 13:47 EST 2024. Contains 370512 sequences. (Running on oeis4.)