A089313 - OEIS

A089313

Write n in binary; a(n) = number represented by second block of 1's from the right.

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 3, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 3, 3, 3, 0, 7, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 0, 3, 3, 3, 3, 1, 3, 3, 0, 7, 7, 7, 0, 15, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 7, 1, 1, 0, 3, 3, 3, 1, 3, 3, 1, 1

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,14

LINKS

Table of n, a(n) for n=0..104.

FORMULA

a(n) = 2^A089310(n)-1. - David Wasserman, Sep 09 2005

EXAMPLE

13 = 1101 so a(13) = 3.

PROG

(PARI) { a(n) = local(b, l, r, c); b=binary(n); l=length(b); while(l&&b[l]==0, l--); while(l&&b[l]==1, l--); while(l&&b[l]==0, l--); r=0; c=0; while(l&&b[l], r+=2^c; l--; c++); r; } for(i=0, 200, print1(a(i), ", ")) (Klasen)

CROSSREFS

Cf. A089309-A089312.

Sequence in context: A035677 A283470 A101941 * A052998 A290174 A344937

Adjacent sequences: A089310 A089311 A089312 * A089314 A089315 A089316

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Dec 22 2003

EXTENSIONS

More terms from David Wasserman and Lambert Klasen (Lambert.Klasen(AT)gmx.net), Sep 09 2005

STATUS

approved