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 A122118 #37 Oct 01 2020 02:45:17
%S A122118 2,7,29,7,641,7,29,7,17,7,29,7,641,7,29,7,97,7,29,7,641,7,29,7,17,7,
%T A122118 29,7,641,7,29,7,193,7,29,7,73,7,29,7,17,7,29,7,641,7,29,7,97,7,29,7,
%U A122118 641,7,29,7,17,7,29,7,641,7,29,7,274568286337,7,29,7,137,7,29,7,17,7,29,7,457
%N A122118 Least prime factor of 2^n + 5^n.
%C A122118 a(n_odd)=7, a(n=2+4k,k=0,1,...)=29, a(64)=274568286337 is unusually large.
%H A122118 Hans Havermann, <a href="/A122118/b122118.txt">Table of n, a(n) for n = 0..1023</a> (terms 0..319 from Antti Karttunen)
%F A122118 a(n) = A020639(A074600(n)). - _Antti Karttunen_, Nov 02 2018
%t A122118 Table[FactorInteger[2^n+5^n][[1,1]],{n,0,80}] (* or *) Riffle[Table[ FactorInteger[2^n+5^n][[1,1]],{n,0,80,2}],7] (* The second program is faster *) (* _Harvey P. Dale_, Mar 02 2015 *)
%o A122118 (PARI) A122118(n) = { my(k=(2^n+5^n)); forprime(p=if(64==n,274568286337,2),k,if(!(k%p),return(p))); }; \\ _Antti Karttunen_, Nov 02 2018
%Y A122118 Cf. A020639, A074600 (2^n + 5^n), A094475 (primes of form 2^n + 5^n), A122119, A337429.
%Y A122118 Cf. also A094473.
%K A122118 nonn
%O A122118 0,1
%A A122118 _Zak Seidov_, Oct 19 2006