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 A333474 #12 Mar 24 2020 02:32:37 %S A333474 0,1,2,3,9,98,135,200,665,1782,4230,4521,6815,17010,19635,30338,31365, %T A333474 35427,49555,96619,102897,157850,193734,273050,393225,449217,477333, %U A333474 483310,493350,534465,661815,918918,947925,1050858,1114690,1134945,1204686,1350990,1428105 %N A333474 Numbers k such that 2^k + 1 is divisible by the sum of its decimal digits. %C A333474 Numbers k such that A000051(k) is in A005349. %e A333474 9 is in the sequence, because 2^9 + 1 = 513 is divisible by 5 + 1 + 3. %o A333474 (Python) %o A333474 print([i for i in range(5000) if (2**i+1)%sum([int(i) for i in str(2**i+1)]) == 0]) %o A333474 (PARI) isok(k) = my(x=2^k+1); !(x % sumdigits(x)); \\ _Michel Marcus_, Mar 23 2020 %Y A333474 Cf. A000051, A005349, A095412. %K A333474 nonn,base %O A333474 1,3 %A A333474 _Daniel Starodubtsev_, Mar 23 2020 %E A333474 More terms from _Giovanni Resta_, Mar 23 2020