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 A193109 #44 Feb 19 2023 04:09:30
%S A193109 0,1,9,3,225,15,65835,1605,19425,2397347205,153535525935
%N A193109 Least k such that 2^x + k produces primes for x=1..n and composite for x=n+1.
%C A193109 All terms except the first four are congruent to 15 mod 30.
%C A193109 a(10) was found in 2005 by _T. D. Noe_ and a(11) was found in the same year by _Don Reble_.
%C A193109 Other known values: a(13) = 29503289812425.
%C A193109 a(12) > 10^13. - _Tyler Busby_, Feb 19 2023
%t A193109 Table[k = 0; While[i = 1; While[i <= n && PrimeQ[2^i + k], i++]; i <= n || PrimeQ[2^i + k], k++]; k, {n, 9}] (* _T. D. Noe_, Jul 21 2011 *)
%o A193109 (PARI) is(k, n) = for(x=1, n, if(!isprime(k+2^x), return(0))); 1;
%o A193109 a(n) = {my(s=2); forprime(p=3, n, if(znorder(Mod(2, p))==(p-1), s*=p)); forstep(k=s*(n>1)/2, oo, s, if(is(k, n) && !isprime(k+2^(n+1)), return(k))); } \\ _Jinyuan Wang_, Jul 30 2020
%Y A193109 Another version of A110096.
%Y A193109 Cf. A008597, A057733, A092506, A104070, A144487.
%K A193109 nonn,more
%O A193109 1,3
%A A193109 _Arkadiusz Wesolowski_, Jul 21 2011