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 A079428 #9 Mar 26 2025 08:30:44
%S A079428 1,3,5,9,7,35,11,15,25,21,13,175,17,15,22,81,19,175,23,63,22,27,29,
%T A079428 385,49,27,34,45,31,1001,37,45,34,35,38,1225,41,39,46,189,43,715,47,
%U A079428 45,52,51,53,4375,121,63,55,63,59,385,57,135,58,65,61,7007,67,65,68,729,69
%N A079428 Least coprime number m > n with same number of divisors as n, a(1) = 1.
%H A079428 Amiram Eldar, <a href="/A079428/b079428.txt">Table of n, a(n) for n = 1..10000</a>
%F A079428 tau(a(n)) = tau(n), where tau = A000005.
%F A079428 a(A000040(k)) = A079427(A000040(k)) = A000040(k+1).
%t A079428 a[n_] := Module[{d = DivisorSigma[0, n], m = n + 1}, While[! CoprimeQ[m, n] || DivisorSigma[0, m] != d, m++]; m]; a[1] = 1; Array[a, 100] (* _Amiram Eldar_, Mar 26 2025 *)
%o A079428 (PARI) a(n) = if(n == 1, 1, my(d = numdiv(n), m = n + 1); while(gcd(m, n) > 1 || numdiv(m) != d, m++); m); \\ _Amiram Eldar_, Mar 26 2025
%Y A079428 Cf. A000005, A000040, A079427.
%K A079428 nonn
%O A079428 1,2
%A A079428 _Reinhard Zumkeller_, Jan 08 2003