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 A124417 #13 Mar 23 2020 09:46:37
%S A124417 1,1,9,765,765,8325,8325,7757430,428547690,102764221560,694561346985,
%T A124417 108428872433310,379041973928475,34628781572140470,34628781572140470
%N A124417 a(n) = least k such that 2^i*k+1 is prime for 1<=i<=n.
%t A124417 k = 1; Do[If[n < 3, inc = 1,If[n == 3, inc = 3, inc = 15];];If[Mod[k, inc] > 0, k = k + inc - Mod[k, inc]];While[Nand @@ PrimeQ[Table[2^j, {j, n}]*k + 1], k += inc]; Print[k], {n, 1, 15}] (* _Ray Chandler_, Nov 21 2006 *)
%Y A124417 Cf. A005097, A123998, A124041, A124412, A124413, A124414, A124415, A124416.
%K A124417 nonn,more
%O A124417 1,3
%A A124417 _Artur Jasinski_, Nov 02 2006
%E A124417 Edited by _Ray Chandler_, Nov 21 2006
%E A124417 a(10) from _Farideh Firoozbakht_, Nov 25 2006
%E A124417 a(11)-a(15) from _Giovanni Resta_, Apr 24 2019