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
Keywords
Examples
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.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
- Wikipedia, Primorial number system.
- Index entries for sequences related to primorial base.
Programs
-
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]