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 A372743 #6 May 12 2024 11:19:52
%S A372743 4,9,25,49,121,27,169,289,24,361,529,54,841,961,36,1369,1681,1849,
%T A372743 2209,2809,343,3481,3721,4489,5041,5329,6241,100,6889,189,7921,72,
%U A372743 9409,112,10201,10609,11449,11881,686,12769,16129,17161,225,18769,19321,196,22201,160
%N A372743 a(n) is the unique number m such that A336563(m) = A372742(n).
%C A372743 Includes all the squares of primes (A001248).
%H A372743 Amiram Eldar, <a href="/A372743/b372743.txt">Table of n, a(n) for n = 1..10000</a>
%F A372743 A336563(a(n)) = A372742(n).
%t A372743 f[p_, e_] := (p^(e + 1) - 1)/(p - 1) - 1; s[1] = 0; s[n_] := Times @@ f @@@ FactorInteger[n] - n; seq[max_] := Module[{v = w = Table[0, {max}], i}, Do[i = s[k]; If[1 <= i <= max, v[[i]]++; w[[i]] = k], {k, 1, max^2}]; w[[Position[v, 1] // Flatten]]]; seq[200]
%o A372743 (PARI) s(n) = {my(f = factor(n)); prod(i = 1, #f~, (f[i, 1]^(f[i, 2] + 1) - 1)/(f[i, 1] -1) - 1) - n;}
%o A372743 lista(nmax) = {my(v = w = vector(nmax), i); for(k = 1, nmax^2, i = s(k); if(i > 0 && i <= nmax, v[i]++; w[i] = k)); for(k = 1, nmax, if(v[k] == 1, print1(w[k], ", ")));}
%Y A372743 Cf. A336563, A372742.
%Y A372743 A001248 is a subsequence.
%Y A372743 Similar sequences: A357313, A357325, A361420.
%K A372743 nonn
%O A372743 1,1
%A A372743 _Amiram Eldar_, May 12 2024