This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A333422 #18 Jun 28 2023 12:36:37 %S A333422 29,37,137,181,733,743,769,977,1013,1031,1033,1049,5107,5119,5171, %T A333422 5179,5233,5273,5297,5323,5387,5393,5399,5407,5437,5441,5449,5471, %U A333422 5477,5483,6571,6607,6689,6691,6709,6719,6733,6763,6803,6823,6829,6907,6947,6949,40343 %N A333422 Factorial base emirps: prime numbers whose factorial base reversal is a different prime. %H A333422 Amiram Eldar, <a href="/A333422/b333422.txt">Table of n, a(n) for n = 1..10000</a> %H A333422 Wikipedia, <a href="http://en.wikipedia.org/wiki/Factorial_number_system">Factorial number system</a>. %H A333422 <a href="/index/Fa#facbase">Index entries for sequences related to factorial base representation</a>. %e A333422 29 is a term since it is a prime number and its representation in factorial base is 1021, whose reversal, 1201, is the factorial base representation of another prime number, 37. %t A333422 max = 8; bases = Range[max, 2, -1]; nmax = max! - 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] %Y A333422 Cf. A007623, A046807, A108731, A333421. %Y A333422 Cf. A006567, A080790. %K A333422 nonn,base %O A333422 1,1 %A A333422 _Amiram Eldar_, Mar 20 2020