A190609 a(1)=a(2)=1; thereafter a(n) = 3*(a(ceiling(n/2))-a(floor(n/2))).

1, 1, 0, 0, -3, 0, 0, 0, -9, 0, 9, 0, 0, 0, 0, 0, -27, 0, 27, 0, 27, 0, -27, 0, 0, 0, 0, 0, 0, 0, 0, 0, -81, 0, 81, 0, 81, 0, -81, 0, 81, 0, -81, 0, -81, 0, 81, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -243, 0, 243, 0, 243, 0, -243, 0, 243, 0, -243, 0, -243, 0, 243, 0, 243, 0, -243, 0, -243, 0, 243, 0

Offset

1,5

Links

Table of n, a(n) for n=1..88.

Maple

f:=proc(n) option remember; local r; r:=3;
if n <= 2 then 1 else r*(f(ceil(n/2))-f(floor(n/2))); fi; end;

Mathematica

a[1]=a[2]=1; a[n_]:=a[n]=3(a[Ceiling[n/2]]-a[Floor[n/2]]); Array[a, 90] (* Harvey P. Dale, Jul 20 2020 *)

Crossrefs

Cf. A190608, A190610.

Sequence in context: A342590 A209436 A229121 * A370146 A325974 A057389

Adjacent sequences: A190606 A190607 A190608 * A190610 A190611 A190612

Keyword

sign

Author

N. J. A. Sloane, May 13 2011, based on a posting by Benoit CLOITRE to the Sequence Fans Mailing List, Apr 29 2011

Status

approved