A063127 Composite numbers which in base 2 contain their largest proper factor as a substring.

4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 91, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128

Offset

1,1

Comments

This is also the set of highest rolls that can be made with some number of platonic dice (dice which are platonic solids, considered to be the most "fair" dice). For instance, 22 is the highest roll with a die which is a dodecahedron, a cubic die, and a tetrahedral die. - Joshua R. Tint, Sep 08 2020

Contains every even number > 2. Odd terms are A063131. - David A. Corneth, Sep 09 2020

Links

Table of n, a(n) for n=1..65.

Example

55 is in the sequence as 55 = 110111_2 and the largest proper divisor of 55 is 11 and 11 = 1011_2 which is contained in 110111_2. - David A. Corneth, Sep 08 2020

Mathematica

Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ FromDigits[ IntegerDigits[ n, 2 ] ] ], ToString[ FromDigits[ IntegerDigits[ Divisors[ n ] [ [ -2 ] ], 2 ] ] ] ] != {}, Print[ n ] ], {n, 2, 150} ]

Crossrefs

Cf. A062238, A063131.

Sequence in context: A324705 A032583 A175074 * A272651 A103517 A163300

Adjacent sequences: A063124 A063125 A063126 * A063128 A063129 A063130

Keyword

nonn,easy,base

Author

Robert G. Wilson v, Aug 08 2001

Status

approved