|
Search: id:A063138
|
|
|
| A063138 |
|
Composite numbers not divisible by 2, 3, 5 or 7 which in base 2 contain their largest proper factor as a substring. |
|
+0
2
|
|
| 407, 493, 893, 1189, 1343, 1403, 1643, 1681, 1961, 3151, 3223, 4063, 4579, 7087, 7597, 7979, 8791, 9167, 10579, 11227, 13303, 14219, 15487, 16147, 23479, 24341, 25751, 26101, 27571, 28757, 30461, 30607, 33431, 34093, 35417, 36349, 39917
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
EXAMPLE
|
407 is in the sequence because 407_d = 110010111_b and its largest proper divisor is 37_d = 100101_b is a substring. Also 407 is not prime nor congruent to 0 (modulo either 2, 3, 5 or 7).
|
|
MATHEMATICA
|
a = {}; Do[ If[ !PrimeQ[n] && Sort[Mod[n, {3, 5, 7}]][[1]] != 0 && StringPosition[ ToString[ FromDigits[ IntegerDigits[n, 2]]], ToString[ FromDigits[ IntegerDigits[ Divisors[n][[ -2]], 2]]]] != {}, a = Append[a, n]], {n, 3, 39960, 2}]; a
|
|
CROSSREFS
|
Cf. A062238.
Sequence in context: A117836 A135791 A132362 this_sequence A118327 A063145 A067674
Adjacent sequences: A063135 A063136 A063137 this_sequence A063139 A063140 A063141
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 08 2001. Corrected Nov 13 2002.
|
|
|
Search completed in 0.002 seconds
|
