

A004780


Binary expansion contains 2 adjacent 1's.


7



3, 6, 7, 11, 12, 13, 14, 15, 19, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 35, 38, 39, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 67, 70, 71, 75, 76, 77, 78, 79, 83, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100
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OFFSET

1,1


COMMENTS

Complement of A003714. It appears that n is in the sequence if and only if C(3n,n) is even.  Benoit Cloitre, Mar 09 2003
Since the binary representation of these numbers contains two adjacent 1's, so for these values of n, we will have (n XOR 2n XOR 3n) != 0, and thus a two player Nim game with three heaps of (n, 2n, 3n) stones will be a winning configuration for the first player.  V. Raman, Sep 17 2012
A048728(a(n)) > 0.  Reinhard Zumkeller, May 13 2014


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Index entries for sequences related to binary expansion of n


FORMULA

a(n) ~ n.  Charles R Greathouse IV, Sep 19 2012


PROG

(PARI) is(n)=bitand(n, n+n)>0 \\ Charles R Greathouse IV, Sep 19 2012
(Haskell)
a004780 n = a004780_list !! (n1)
a004780_list = filter ((> 1) . a048728) [1..]
 Reinhard Zumkeller, May 13 2014


CROSSREFS

Cf. A005809, A048728, A242408.
Complement: A003714.
Subsequences (apart from any initial zeroterm): A001196, A004755, A004767, A033428, A277335.
Sequence in context: A292608 A028754 A028795 * A292046 A051146 A136272
Adjacent sequences: A004777 A004778 A004779 * A004781 A004782 A004783


KEYWORD

nonn,easy,base


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Offset corrected by Reinhard Zumkeller, Jul 28 2010


STATUS

approved



