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 A231476 #16 Jan 17 2022 00:31:56 %S A231476 2,7,13,19,31,151,163,211,223,229,241,271,349,367,439,601,607,613,631, %T A231476 643,673,727,733,859,907,937,997,1021,1033,1039,1051,1093,1117,1123, %U A231476 1129,1153,1321,1327,1399,1423,1429,1609,1627,1657,1669,1741,1747,1759,1777,1789,1831,1867,1933,1951,1993,1999 %N A231476 Primes whose base-3 representation is also the base-6 representation of a prime. %C A231476 This sequence is part of a two-dimensional array of sequences, given in the LINK, based on this same idea for any two different bases b, c > 1. Sequence A235265 and A235266 are the most elementary ones in this list. Sequences A089971, A089981 and A090707 through A090721, and sequences A065720 - A065727, follow the same idea with one base equal to 10. %C A231476 Subsequence of A045375 ⊂ A045331. %H A231476 Harvey P. Dale, <a href="/A231476/b231476.txt">Table of n, a(n) for n = 1..1000</a> %H A231476 M. F. Hasler, <a href="https://docs.google.com/document/d/10IM7fcAbB2tqRGuwfGvuEGUzD_IXbgXPDK0tfxN4M3o/pub">Primes whose base c expansion is also the base b expansion of a prime</a> %e A231476 7 = 21_3 and 21_6 = 13 are both prime. %t A231476 Select[Prime[Range[400]],PrimeQ[FromDigits[ IntegerDigits[#, 3], 6]] &] (* _Harvey P. Dale_, Sep 29 2016 *) %o A231476 (PARI) is(p,b=6,c=3)=isprime(vector(#d=digits(p,c),i,b^(#d-i))*d~)&&isprime(p) \\ Note: This code is only valid for b>c. %Y A231476 Cf. A235469, A235265, A235266, A235473, A152079, A235461 - A235482, A065720 ⊂ A036952, A065721 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924. See the LINK for further cross-references. %K A231476 nonn,base %O A231476 1,1 %A A231476 _M. F. Hasler_, Jan 12 2014