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A080788
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Primes that are still primes when turned upsided down.
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1
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11, 19, 61, 101, 109, 181, 199, 601, 619, 661, 1019, 1061, 1091, 1109, 1181, 1601, 1609, 1669, 1699, 1811, 1901, 1999, 6011, 6091, 6101, 6199, 6619, 6661, 6689, 6691, 6899, 6991, 10061, 10069, 10091, 10691, 10861, 10909, 11069, 11681, 11909, 16001, 16091
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| P. Giannopoulos, The Brainteasers, unpublished.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
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PROG
| (Haskell)
import Data.List (unfoldr)
a048890 n = a048890_list !! (n-1)
a048890_list = filter f a000040_list where
f x = all (`elem` [0, 1, 6, 8, 9]) ds && x' /= x && a010051 x' == 1
where x' = foldl c 0 ds
c v 6 = 10*v + 9; c v 9 = 10*v + 6; c v d = 10*v + d
ds = unfoldr d x
d z = if z == 0 then Nothing else Just $ swap $ divMod z 10
-- Reinhard Zumkeller, Nov 18 2011
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CROSSREFS
| Cf. A057770.
Cf. A007597.
Sequence in context: A139602 A080789 A057770 * A089032 A106231 A107637
Adjacent sequences: A080785 A080786 A080787 * A080789 A080790 A080791
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KEYWORD
| base,easy,nonn
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AUTHOR
| Giannopoulos P. (pgiannop1(AT)yahoo.com), Mar 12 2003
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EXTENSIONS
| Missing 1669 and 6689 inserted by Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 18 2011
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