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 A235637 #15 Nov 02 2023 10:39:16 %S A235637 2,3,5,19,61,89,127,131,173,211,229,257,281,383,397,421,463,467,523, %T A235637 547,593,617,719,757,761,859,883,911,953,967,971,1069,1097,1153,1163, %U A235637 1181,1303,1307,1429,1433,1471,1489,1531,1583,1597,1723,1741,1867,1877,1951,1979,1993,2437 %N A235637 Primes whose base-7 representation also is the base-6 representation of a prime. %C A235637 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 A235637 Robert Price, <a href="/A235637/b235637.txt">Table of n, a(n) for n = 1..14278</a> %H A235637 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 A235637 E.g., 19 = 25_7 and 25_6 = 17 are both prime. %o A235637 (PARI) is(p,b=6,c=7)=vecmax(d=digits(p,c))<b&&isprime(vector(#d,i,b^(#d-i))*d~)&&isprime(p) %o A235637 (PARI) forprime(p=1,3e3,is(p,7,6)&&print1(vector(#d=digits(p,6),i,7^(#d-i))*d~,",")) \\ To produce the terms, this is more efficient than to select them using straightforwardly is(.)=is(.,6,7) %Y A235637 Cf. A235636, A235265, A235266, A152079, A235461 - A235482, A065720 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924, A235615 - A235639. See the LINK for further cross-references. %K A235637 nonn,base %O A235637 1,1 %A A235637 _M. F. Hasler_, Jan 13 2014