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 A070029 #8 Jul 18 2021 12:24:45 %S A070029 2,3,5,7,23,223,227,353,2333,2777,3323,7727,27527,33377,33773,35537, %T A070029 35573,35753,37337,52727,53777,55337,55373,55733,57557,57737,57773, %U A070029 73553,73757,75227,75353,75377,75533,75557,75773,77573,222557,222773 %N A070029 Primes with only prime digits and whose initial, all intermediate and final iterated sums of digits are primes. %C A070029 This sequence is the intersection of A062088 and A070027. %e A070029 53777 is a term because 53777 is a prime with only prime digits and 5+3+7+7+7=29, 2+9=11 and 1+1=2 are all prime. %t A070029 iifpQ[n_]:=AllTrue[NestWhileList[Total[IntegerDigits[#]]&,n,#>9&],PrimeQ]; Select[Prime[Range[20000]],AllTrue[IntegerDigits[#],PrimeQ]&&iifpQ[#]&] (* _Harvey P. Dale_, Jul 18 2021 *) %Y A070029 Cf. A070027, A062088 (only first sum of digits is necessarily prime). %K A070029 base,nonn %O A070029 1,1 %A A070029 _Rick L. Shepherd_, Apr 21 2002