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A004780 Binary expansion contains 2 adjacent 1's. 10
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 (list; graph; refs; listen; history; text; internal format)
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 !! (n-1)

a004780_list = filter ((> 1) . a048728) [1..]

-- Reinhard Zumkeller, May 13 2014

CROSSREFS

Cf. A005809, A048728, A242408.

Complement: A003714.

Subsequences (apart from any initial zero-term): 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

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)