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 A235469 #15 Nov 01 2023 23:21:00 %S A235469 2,13,43,73,223,1777,2593,2887,3037,3067,3109,7993,9157,9337,10597, %T A235469 17077,17107,17137,17317,17359,18229,18661,46663,48247,49297,49537, %U A235469 54517,54727,54877,54907,54949,55987,56197,56209,56239,57097,63589,63727,64879,65089,65101,95089,95917,96157 %N A235469 Primes whose base-6 representation also is the base-3 representation of a prime. %C A235469 This sequence is part of the two-dimensional array of sequences 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 A235469 For further motivation and cross-references, see sequence A235265 which is the main entry for this whole family of sequences. %H A235469 Robert Price, <a href="/A235469/b235469.txt">Table of n, a(n) for n = 1..1959</a> %H A235469 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 A235469 E.g., 13 = 21_6 and 21_3 = 7 are both prime. %o A235469 (PARI) is(p,b=3,c=6)=vecmax(d=digits(p,c))<b&&isprime(vector(#d,i,b^(#d-i))*d~)&&isprime(p) %o A235469 (PARI) forprime(p=1,1e3,is(p,6,3)&&print1(vector(#d=digits(p,3),i,6^(#d-i))*d~,",")) \\ To produce the terms, this is more efficient than to select them using straightforwardly is(.)=is(.,3,6) %Y A235469 Cf. A065720 ⊂ A036952, A065721 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924, A235461 - A235482. See the LINK for further cross-references. %K A235469 nonn,base %O A235469 1,1 %A A235469 _M. F. Hasler_, Jan 12 2014