|
| |
|
|
A048889
|
|
Composite numbers not ending in zero that yield a prime when turned upside down.
|
|
2
| |
|
|
68, 116, 118, 161, 166, 169, 188, 608, 616, 1006, 1018, 1066, 1081, 1096, 1106, 1108, 1118, 1169, 1186, 1606, 1618, 1808, 1816, 1898, 1916, 1918, 1969, 1981, 1988, 1996, 6001, 6008, 6016, 6098, 6188, 6191, 6196, 6616, 6668, 6698, 6808, 6809, 6881, 6896
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1048 (all terms < 1000000)
|
|
|
EXAMPLE
| 68 is not prime, yet when turned upside down gives 89 which is prime.
|
|
|
PROG
| (Haskell)
import Data.List (intersect)
import Numeric (readInt)
import Data.Char (digitToInt)
a048889 n = a048889_list !! (n-1)
a048889_list = filter f a002808_list where
f n = n `mod` 10 > 0 &&
null ("23547" `intersect` show n) &&
(a010051 (fst $ head $ readInt 10 (const True) ud $ ns) == 1)
where ns = reverse $ show n
ud '6' = 9
ud '9' = 6
ud z = digitToInt z
-- Reinhard Zumkeller, Aug 11 2011
|
|
|
CROSSREFS
| Cf. A002808, A010051.
Sequence in context: A044036 A045268 A039540 * A111379 A044191 A044572
Adjacent sequences: A048886 A048887 A048888 * A048890 A048891 A048892
|
|
|
KEYWORD
| base,easy,nonn,nice
|
|
|
AUTHOR
| G. L. Honaker, Jr. (honak3r(AT)gmail.com)
|
| |
|
|
