A089310 - OEIS

A089310

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

0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 2, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 2, 2, 2, 0, 3, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 0, 2, 2, 2, 2, 1, 2, 2, 0, 3, 3, 3, 0, 4, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 3, 1, 1, 0, 2, 2, 2

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OFFSET

0,14

LINKS

Robert Israel, Table of n, a(n) for n = 0..10000

EXAMPLE

13 = 1101 so a(13) = 2.

MAPLE

f:= proc(n) local t, q, r;

r:= 0: t:= n;

while t::even do t:= t/2 od;

while t::odd do t:= (t-1)/2 od;

if t = 0 then return 0 fi;

while t::even do t:= t/2 od;

while t::odd do r:= r+1; t:= (t-1)/2 od;

end proc:

f(0):= 0:

map(f, [$0..100]); # Robert Israel, Aug 03 2025

PROG

(PARI) a(n)=my(b, c, s); if(n==0, return(0)); b=binary(n); c=length(b); while(!b[c], c=c-1); while(c>0&&b[c], c=c-1); if(c<=0, 0, while(!b[c], c=c-1); s=0; while(c>0&&b[c], c=c-1; s=s+1); s) /* Ralf Stephan, Feb 01 2004 */

CROSSREFS

Cf. A089309, A089311, A089312, A089313.

Sequence in context: A364044 A269247 A330268 * A129753 A356324 A307247

Adjacent sequences: A089307 A089308 A089309 * A089311 A089312 A089313

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Dec 22 2003

EXTENSIONS

More terms from Ralf Stephan, Feb 01 2004

STATUS

approved