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 A235477 #12 May 08 2021 19:28:10 %S A235477 2,31,47,59,103,107,173,179,181,199,211,227,229,233,367,409,443,463, %T A235477 487,701,743,757,823,827,877,911,919,967,1009,1123,1163,1291,1321, %U A235477 1367,1373,1447,1493,1571,1583,1597,1609,1627,1657,1669,1721,1831,1933,1987 %N A235477 Primes whose base-2 representation also is the base-7 representation of a prime. %C A235477 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 A235477 For further motivation and cross-references, see sequence A235265 which is the main entry for this whole family of sequences. %C A235477 A subsequence of A027697, A015919, A197636 (conjectural). %H A235477 Harvey P. Dale, <a href="/A235477/b235477.txt">Table of n, a(n) for n = 1..1000</a> %H A235477 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 A235477 31 = 11111_2 and 11111_7 = 2801 are both prime, so 31 is a term. %t A235477 Select[Prime[Range[300]],PrimeQ[FromDigits[IntegerDigits[#,2],7]]&] (* _Harvey P. Dale_, May 08 2021 *) %o A235477 (PARI) is(p,b=7)=isprime(vector(#d=binary(p),i,b^(#d-i))*d~)&&isprime(p) %Y A235477 Cf. A235464 ⊂ A077721, A235475, A152079, A235266, A065720 ⊂ A036952, A065721 - A065727, A089971 ⊂ A020449, A089981, A090707 - A091924, A235394, A235395, A235461 - A235482. See the LINK for further cross-references. %K A235477 nonn,base %O A235477 1,1 %A A235477 _M. F. Hasler_, Jan 12 2014