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 A235627 #12 Nov 02 2023 10:39:20 %S A235627 2,3,7,17,23,31,53,71,73,79,101,109,113,127,151,157,197,199,359,401, %T A235627 409,449,463,521,541,557,743,863,1033,1039,1103,1151,1193,1229,1451, %U A235627 1487,1499,1543,2423,2521,2549,2621,2753,2857,2909,2957,3089,3257,3313,3511,3529,3593 %N A235627 Primes whose base-7 representation also is the base-5 representation of a prime. %C A235627 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. %H A235627 Robert Price, <a href="/A235627/b235627.txt">Table of n, a(n) for n = 1..13736</a> %H A235627 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 A235627 Both 17 = 23_7 and 23_5 = 13 are prime. %o A235627 (PARI) is(p,b=5,c=7)=vecmax(d=digits(p,c))<b&&isprime(vector(#d,i,b^(#d-i))*d~)&&isprime(p) %o A235627 (PARI) forprime(p=1,3e3,is(p,7,5)&&print1(vector(#d=digits(p,5),i,7^(#d-i))*d~,",")) \\ To produce the terms, this is more efficient than to select them using straightforwardly is(.)=is(.,5,7) %Y A235627 Cf. A235635, A235265, A235266, A152079, A235461 - A235482, A065720 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924, A235615 - A235639. See the LINK for further cross-references. %K A235627 nonn,base %O A235627 1,1 %A A235627 _M. F. Hasler_, Jan 13 2014