A214584 -id:A214584 - cp's OEIS frontend

A217039 Primes having only {4, 5, 7} as digits.

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

Offset: 1

Jonathan Vos Post, Sep 24 2012

These are the primes in A214584. Primes whose numerals are all written (san serif) with at least one right or acute angle.

Cf. A079651, A079652, A214584.

Cf. A036953, A260044, A260267 - A260271, A199325 - A199329, A061247, A199340 - A199349.

[p: p in PrimesUpTo(450000) | Intseq(p) subset [4,5,7]]; // Bruno Berselli, Sep 25 2012

Select[Flatten[Table[FromDigits/@Tuples[{4,5,7},n],{n,6}]],PrimeQ] (* Bruno Berselli, Sep 25 2012 *)

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

A000040 INTERSECTION A214584.

A217124 Semiprimes whose decimal representation has only digits in {4,5,7}.

Original entry on oeis.org

4, 55, 57, 74, 77, 445, 447, 454, 545, 554, 745, 755, 4474, 4555, 4574, 4577, 4747, 4754, 4757, 4777, 5447, 5455, 5545, 5554, 5747, 5755, 5774, 5777, 7445, 7447, 7454, 7555, 7745, 7747, 7754, 44477, 44554, 44557, 44747, 44755, 45447, 45454, 45455, 45457

Offset: 1

Jonathan Vos Post, Sep 26 2012

Crooked semiprimes. This is to A217048 as integers all of whose numerals are written (san serif) with at least one right or acute angle (A214584) are to numbers using only the curved digits 0, 3, 6, 8 and 9 (A072960). This is to crooked primes (A217039) as semiprimes (A001358) are to primes (A000040).

			4555 = 5 * 911 is semiprime.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A001358, A072960, A214584.

SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Flatten[Table[FromDigits /@ Tuples[{4, 5, 7}, n], {n, 5}]], SemiPrimeQ] (* T. D. Noe, Sep 27 2012 *)
Select[Flatten[Table[FromDigits/@Tuples[{4,5,7},n],{n,5}]],PrimeOmega[ #] == 2&] (* Harvey P. Dale, Sep 21 2016 *)

A001358 INTERSECTION A214584.

Corrected and extended by T. D. Noe, Sep 27 2012

cp's OEIS Frontend

A217039 Primes having only {4, 5, 7} as digits.

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