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A019546
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Primes whose digits are primes.
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102
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2, 3, 5, 7, 23, 37, 53, 73, 223, 227, 233, 257, 277, 337, 353, 373, 523, 557, 577, 727, 733, 757, 773, 2237, 2273, 2333, 2357, 2377, 2557, 2753, 2777, 3253, 3257, 3323, 3373, 3527, 3533, 3557, 3727, 3733, 5227, 5233, 5237, 5273, 5323, 5333, 5527, 5557
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OFFSET
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1,1
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COMMENTS
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Ribenboim mentioned in 2000 the following number as largest known term: 72323252323272325252 * (10^3120 - 1) / (10^20 - 1) + 1. It has 3120 digits, and was discovered by Harvey Dubner in 1992. Larger terms are 22557252272*R(15600)/R(10) and 2255737522*R(15600) where R(n) denotes the n-th repunit (see A002275): Both have 15600 digits and were found in 2002, also by Dubner (see Weisstein link). David Broadhurst reports in 2003 an even longer number with 82000 digits: (10^40950+1) * (10^20055+1) * (10^10374 + 1) * (10^4955 + 1) * (10^2507 + 1) * (10^1261 + 1) * (3*R(1898) + 555531001*10^940 - R(958)) + 1, see link. - Reinhard Zumkeller, Jan 13 2012
The smallest and largest primes that use exactly once the four prime decimal digits are respectively a(27)= 2357 and a(54) = 7523. - Bernard Schott, Apr 27 2023
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REFERENCES
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Paulo Ribenboim, Prime Number Records (Chap 3), in 'My Numbers, My Friends', Springer-Verlag 2000 NY, page 76.
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LINKS
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József Bölcsföldi and György Birkás, Golden ratio prime numbers, International Journal of Engineering Science Invention (2018) Vol. 6 Issue 12, 82-85.
Chris K. Caldwell and G. L. Honaker, Jr., 2357, Prime Curios!
Chris K. Caldwell and G. L. Honaker, Jr., 7523, Prime Curios!
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MATHEMATICA
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Select[Prime[Range[700]], Complement[IntegerDigits[#], {2, 3, 5, 7}] == {} &] (* Alonso del Arte, Aug 27 2012 *)
Select[Prime[Range[700]], AllTrue[IntegerDigits[#], PrimeQ] &] (* Ivan N. Ianakiev, Jun 23 2018 *)
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PROG
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(PARI) is_A019546(n)=isprime(n) & !setminus(Set(Vec(Str(n))), Vec("2357")) \\ M. F. Hasler, Jan 13 2012
(PARI) print1(2); for(d=1, 4, forstep(i=1, 4^d-1, [1, 1, 2], p=sum(j=0, d-1, 10^j*[2, 3, 5, 7][(i>>(2*j))%4+1]); if(isprime(p), print1(", "p)))) \\ Charles R Greathouse IV, Apr 29 2015
(Haskell)
a019546 n = a019546_list !! (n-1)
a019546_list = filter (all (`elem` "2357") . show )
([2, 3, 5] ++ (drop 2 a003631_list))
-- Or, much more efficient:
a019546_list = filter ((== 1) . a010051) $
[2, 3, 5, 7] ++ h ["3", "7"] where
h xs = (map read xs') ++ h xs' where
xs' = concat $ map (f xs) "2357"
f xs d = map (d :) xs
(Magma) [p: p in PrimesUpTo(5600) | Set(Intseq(p)) subset [2, 3, 5, 7]]; // Bruno Berselli, Jan 13 2012
(Python)
from itertools import product
from sympy import isprime
A019546_list = [2, 3, 5, 7]+[p for p in (int(''.join(d)+e) for l in range(1, 5) for d in product('2357', repeat=l) for e in '37') if isprime(p)] # Chai Wah Wu, Jun 04 2021
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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R. Muller
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EXTENSIONS
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STATUS
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approved
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