A333425 Primorial base emirps: prime numbers whose primorial base reversal is a different prime.

227, 283, 2339, 2351, 2357, 2393, 2767, 2777, 2789, 2797, 2801, 2833, 2851, 2861, 30059, 30089, 30161, 30169, 30187, 30197, 30223, 30293, 30313, 30319, 30389, 30391, 30449, 30467, 30509, 30517, 30559, 30631, 30649, 30677, 30689, 30727, 30763, 30781, 30803, 30851

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Wikipedia, Primorial number system.

Index entries for sequences related to primorial base.

Example

227 is a term since it is a prime number and its representation in primorial base is 10221, whose reversal, 12201, is the primorial base representation of another prime number, 283.

Mathematica

max = 7; bases = Prime @ Range[max, 1, -1]; nmax = Times @@ bases - 1; emirpQ[n_] := PrimeQ[n] && Module[{d = IntegerDigits[n, MixedRadix[bases]]}, r = Reverse @ d; IntegerDigits[(m = FromDigits[r, MixedRadix[bases]]), MixedRadix[bases]] == r && m != n && PrimeQ[m]]; Select[Range[nmax], emirpQ]

Crossrefs

Cf. A049345, A235168, A333424.

Cf. A006567, A080790, A333422.

Sequence in context: A078765 A179141 A259059 * A142261 A117458 A252026

Adjacent sequences: A333422 A333423 A333424 * A333426 A333427 A333428

Keyword

nonn

Author

Amiram Eldar, Mar 20 2020

Status

approved