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 A172411 #14 Aug 16 2025 14:58:57
%S A172411 1,2,5,10
%N A172411 Numbers k such that 2^k+9 and 2^k+27 are prime.
%C A172411 No further terms between 10 and 5000. - _R. J. Mathar_, Feb 07 2010
%C A172411 No further terms to 100000. Expected number of remaining terms: (zeta(2) - 1 - 1/4 - ... - 1/100000^2)/log^2 2 ~= 0.00002. - _Charles R Greathouse IV_, Mar 25 2010
%F A172411 A057196 INTERSECT A157007 - _R. J. Mathar_, Feb 07 2010
%e A172411 a(1)=1 because 2^1+3^2=11 and 2^1+3^3=29 are prime.
%t A172411 Select[Range[10],AllTrue[2^#+{9,27},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, May 28 2016 *)
%o A172411 (PARI) is(n)=isprime(2^n+9) && isprime(2^n+27) \\ _Charles R Greathouse IV_, Sep 06 2016
%K A172411 nonn,less,more
%O A172411 1,2
%A A172411 _Juri-Stepan Gerasimov_, Feb 02 2010