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A217039
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Primes whose decimal representation has only digits in {4,5,7}.
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4
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5, 7, 47, 457, 547, 557, 577, 757, 4447, 4457, 4547, 5477, 5557, 7457, 7477, 7547, 7577, 7757, 44777, 45557, 45757, 47777, 54547, 54577, 55457, 55547, 57457, 57557, 74747, 75557, 75577, 77447, 77477, 77557, 77747, 444547, 444557, 445447, 445477, 445747, 447757
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OFFSET
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1,1
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COMMENTS
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These could be called crooked primes. These are the primes in A214584. Primes whose numerals are all written (san serif) with at least one right or acute angle.
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LINKS
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FORMULA
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MATHEMATICA
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Select[Flatten[Table[FromDigits/@Tuples[{4, 5, 7}, n], {n, 6}]], PrimeQ] (* Bruno Berselli, Sep 25 2012 *)
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PROG
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(Magma) [p: p in PrimesUpTo(450000) | Intseq(p) subset [4, 5, 7]]; // Bruno Berselli, Sep 25 2012
(PARI) A217039(n=50, show=0, L=[4, 5, 7])={for(d=1, 1e9, my(t, u=vector(d, i, 10^(d-i))~); forvec(v=vector(d, i, [if(i==d&&d>1, 3/*must end in 7*/, 1), #L]), ispseudoprime(t=vecextract(L, v)*u)||next; show&&print1(t", "); n--||return(t)))} \\ Syntax updated for newer PARI versions by M. F. Hasler, Jul 25 2015
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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