A129770 a(0) = 0, a(1) = 1; for n>0, a(2n) = 3a(2n-1), a(2n+1) = 3a(2n) - 2a(n-1).

0, 1, 3, 9, 27, 79, 237, 705, 2115, 6327, 18981, 56889, 170667, 511843, 1535529, 4606113, 13818339, 41453607, 124360821, 373078233, 1119234699, 3357691443, 10073074329, 30219185025, 90657555075, 271972551447, 815917654341

Offset

0,3

Links

Table of n, a(n) for n=0..26.

Maple

a:=proc(n) if n=0 or n=1 then n elif n mod 2 = 0 then 3*a(n-1) else 3*a(n-1)-2*a((n-3)/2) fi end: seq(a(n), n=0..31); - Emeric Deutsch, May 19 2007

Mathematica

a[0] = 0; a[1] = 1; a[n_] := If[OddQ@n, 3 a[n - 1] - 2 a[(n - 3)/2], 3 a[n - 1]]; Table[ a[n], {n, 0, 26}] (* Robert G. Wilson v *)

Prog

(PARI) {m=26; v=vector(m+1); v[1]=0; v[2]=1; for(n=2, m, k=3*v[n]; if(n%2==1, k=k-2*v[(n-1)/2]); v[n+1]=k); print(v)} /* Klaus Brockhaus, May 20 2007 */

Crossrefs

Cf. A129772.

Sequence in context: A299108 A304067 A287898 * A134396 A059502 A291006

Adjacent sequences: A129767 A129768 A129769 * A129771 A129772 A129773

Keyword

nonn

Author

Paul Curtz, May 16 2007

Extensions

More terms from Emeric Deutsch, Robert G. Wilson v and Klaus Brockhaus, May 16 2007

Status

approved