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 A282423 #21 Feb 23 2017 10:31:26 %S A282423 3,2,0,13,19,0,427,4,0,0,1,0,802,99412,0,3097,7,0,637,0,0,7225627, %T A282423 30898822,0,0,280134277,0,31705902442,43190647,0,965577112 %N A282423 a(n) = smallest k such that A282026(k) = n, or 0 if no such k exists. %C A282423 a(n) is nonzero if n is in A282429. %C A282423 For n>4 and nonzero a(n), 2*a(n)+3 is in A022004. For n>8 and nonzero a(n), 2*a(n)+3 is also in A153417. For n>16 and nonzero a(n), 2*a(n)+3 is also in A049481. %e A282423 a(10) = 0. Proof: Suppose 10 is a term of A282026. For the corresponding n, 2*n + 1 cannot be divisible by 5 because of A282026’s definition (gcd(10, 2*n + 1) = 1). So 2*n + 1 can be only of the form 10*k + 1, 10*k + 3, 10*k + 7, 10*k + 9. But 10*k + 1 + 2*2, 10*k + 3 + 2*1, 10*k + 7 + 2*4, 10*k + 9 + 2*8 are all composite and 1, 2, 4, 8 are relatively prime to any odd number. Since all of them are smaller than 10, this is the contradiction to the assumption that 10 is the term which is the smallest number for corresponding n. This also proves that a(5*k) = 0 for any k > 1. %Y A282423 Cf. A282026, A282429. %K A282423 nonn,more %O A282423 1,1 %A A282423 _Andrey Zabolotskiy_ and _Altug Alkan_, Feb 14 2017, following a suggestion from _N. J. A. Sloane_