A089311 Write n in binary; a(n) = number of 0's in rightmost block of zeros, after dropping any trailing 0's.

0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 1, 1, 0, 1, 0, 0, 0, 3, 2, 2, 1, 1, 1, 1, 0, 2, 1, 1, 0, 1, 0, 0, 0, 4, 3, 3, 2, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 0, 3, 2, 2, 1, 1, 1, 1, 0, 2, 1, 1, 0, 1, 0, 0, 0, 5, 4, 4, 3, 1, 3, 3, 2, 2, 1, 1, 2, 1, 2, 2, 1, 3, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 0, 4, 3, 3

Offset: 0

Author

N. J. A. Sloane, Dec 22 2003

Keywords

• nonn
• base

Examples

			9 = 1001 so a(9) = 2.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A089309-A089313. Different from A086784.

Programs

Mathematica

bd[n_]:=Module[{s=Split[IntegerDigits[n,2]]},Which[Length[s]<3,0,MemberQ[ Last[s],1],Length[s[[-2]]],True,Length[s[[-3]]]]]; Array[bd,120,0] (* Harvey P. Dale, Dec 29 2013 *)

PARI

a(n)=local(b,c,s):b=binary(n):c=length(b):while(!b[c],c=c-1):while(c>0&&b[c],c=c-1): if(c<=0,0,s=0:while(!b[c],c=c-1:s=s+1):s) \\ Ralf Stephan

Extensions

More terms from Ralf Stephan, Feb 01 2004