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 A152580 #17 Jan 24 2017 20:40:52 %S A152580 9,51,2403,5764803,33232930569603,1104427674243920646305299203 %N A152580 a(n) = 7^(2^n) + 2. %C A152580 These numbers are divisible by 3. This follows by expanding the binomial (6+1)^(2^n) + 2 to get 6h + 1 + 2 for some h. Therefore 3 divides 7^(2^n) + 2. %F A152580 a(n) = A165425(n+3) + 2. - _R. J. Mathar_, Sep 10 2016 %p A152580 A152580:=n->7^(2^n) + 2: seq(A152580(n), n=0..8); # _Wesley Ivan Hurt_, Jan 22 2017 %o A152580 (PARI) g(a,n) = if(a%2,b=2,b=1);for(x=0,n,y=a^(2^x)+b;print1(y",")) %o A152580 (PARI) a(n) = 7^(2^n) + 2; \\ _Michel Marcus_, Jan 24 2017 %Y A152580 Cf. A165425. %K A152580 nonn,easy %O A152580 0,1 %A A152580 _Cino Hilliard_, Dec 08 2008