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A080788 Primes that are still primes when turned upsided down. 1
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; text; internal format)
OFFSET

1,1

REFERENCES

P. Giannopoulos, The Brainteasers, unpublished.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..11210 (First 1000 terms from Reinhard Zumkeller)

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

CROSSREFS

Cf. A057770.

Cf. A007597.

Sequence in context: A139602 A080789 A057770 * A248802 A290078 A089032

Adjacent sequences:  A080785 A080786 A080787 * A080789 A080790 A080791

KEYWORD

base,easy,nonn

AUTHOR

Giannopoulos P. (pgiannop1(AT)yahoo.com), Mar 12 2003

EXTENSIONS

Missing 1669 and 6689 inserted by Reinhard Zumkeller, Nov 18 2011

STATUS

approved

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Last modified September 19 03:31 EDT 2021. Contains 347550 sequences. (Running on oeis4.)