A115639 First column of divide-and-conquer triangle A115636.

1, 1, 4, 4, 4, 4, 16, 16, 16, 16, 16, 16, 16, 16, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256, 256

Offset

0,3

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Formula

G.f.: (1/(1-x))*( 1/4 + (3/4)*Sum_{k>=1} 4^(k-1)*x^(2^k-2) ).

a(n) = 4^(floor(log_2(n+2)) - 1). - G. C. Greubel, Nov 23 2021

Mathematica

4^(Floor[Log[2, Range[0, 80] +2]] -1) (* G. C. Greubel, Nov 23 2021 *)

Prog

(Magma) [4^(Ilog2(n+2) -1) : n in [0..80] ]; // G. C. Greubel, Nov 23 2021
(Sage) [4^(floor(log(n+2, 2)) -1) for n in (0..80)] # G. C. Greubel, Nov 23 2021

Crossrefs

Cf. A000523, A115636.

Sequence in context: A202686 A134660 A132383 * A242954 A062732 A100777

Adjacent sequences: A115636 A115637 A115638 * A115640 A115641 A115642

Keyword

easy,nonn

Author

Paul Barry, Jan 27 2006

Status

approved