This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A075311 a(1) = 1; for n > 1, a(n) = smallest number m > a(n-1) such that number of 1's in binary expansion of m is not already in the sequence. 5
 1, 3, 5, 6, 9, 10, 12, 15, 17, 18, 20, 23, 24, 27, 29, 30, 33, 34, 36, 39, 40, 43, 45, 46, 48, 51, 53, 54, 57, 58, 60, 65, 66, 68, 71, 72, 75, 77, 78, 80, 83, 85, 86, 89, 90, 92, 96, 99, 101, 102, 105, 106, 108, 113, 114, 116, 120, 127, 129, 130, 132, 135, 136, 139, 141 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If A000120(k) is in sequence then k is not. Differs from A001969: 63 is not included since it has 6 bits set. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Phil Carmody, Re: New sieve and a challenge Jon Perry, New sieve and a challenge EXAMPLE We start with a(1)=1. Then 2 is not included since it has one bit set and 1 is in sequence. Next, 3 is included since it has 2 one bits and 2 is not in sequence. And so on. PROG (PARI) v=vector(1000): v[1]=1: for(curr=2, 1000, e=A000120(curr): if(v[e], continue, v[curr]=1)): for(k=1, 1000, if(v[k], print1(k", "))) (Haskell) a075311 n = a075311_list !! (n-1) a075311_list = 1 : f 2 [1] where    f x ys = if a000120 x `elem` ys then f (x + 1) ys                                    else x : f (x + 1) (x : ys) -- Reinhard Zumkeller, Apr 22 2012 CROSSREFS Cf. A075517. Cf. A217122. Sequence in context: A241571 A080307 A001969 * A032786 A080309 A281746 Adjacent sequences:  A075308 A075309 A075310 * A075312 A075313 A075314 KEYWORD easy,nonn AUTHOR Phil Carmody, Oct 11 2002 EXTENSIONS Edited by Ralf Stephan, Sep 14 2003 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.