A080565 Binary expansion of n has form 11**...*1.

3, 7, 13, 15, 25, 27, 29, 31, 49, 51, 53, 55, 57, 59, 61, 63, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233

Offset: 1

Author

Benoit Cloitre, Feb 22 2003

Keywords

• nonn

Comments

If n>3 is in the sequence so are 2n-1 and 2n+1.

Crossrefs

A004755 = union of A079946 and this sequence.

A diagonal of A246830.

Formula

a(n) = 2^floor(log[2](4*(n-1)))+2*n-1 for n>1, a(1)=3. - Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Feb 22 2003

Equals 2 * A004760(n) + 1. - Ralf Stephan, Sep 16 2003