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 A231478 #16 Jan 17 2022 00:32:12 %S A231478 2,7,13,31,37,43,67,73,97,193,283,307,379,457,487,499,577,619,643,727, %T A231478 733,757,829,1297,1321,1429,1447,1609,1669,1693,2011,2083,2137,2251, %U A231478 2269,2347,2539,2803,2857,2953,2971 %N A231478 Primes whose base-3 representation is also the base-8 representation of a prime. %C A231478 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. %H A231478 Giovanni Resta, <a href="/A231478/b231478.txt">Table of n, a(n) for n = 1..10000</a> %H A231478 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 A231478 13 = 111_3 and 111_8 = 73 are both prime, so 13 is a term. %t A231478 Select[Prime@Range@500, PrimeQ@FromDigits[IntegerDigits[#, 3], 8] &] (* _Giovanni Resta_, Sep 12 2019 *) %o A231478 (PARI) is(p,b=8,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 A231478 Cf. A235471, A235265, A235266, A152079, A235461 - A235482, A065720 ⊂ A036952, A065721 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924. See the LINK for further cross-references. %K A231478 nonn,base %O A231478 1,1 %A A231478 _M. F. Hasler_, Jan 12 2014