A356078 -id:A356078 - cp's OEIS frontend

A359964 Refactorable numbers (A033950) having more divisors than all smaller refactorable numbers.

1, 2, 8, 12, 24, 36, 60, 180, 240, 360, 720, 1260, 1680, 3360, 5040, 10080, 15120, 20160, 25200, 30240, 55440, 100800, 110880, 221760, 277200, 443520, 665280, 720720, 1108800, 1441440, 2494800, 2882880, 3603600, 5765760, 8648640, 12972960, 14414400, 25945920, 28828800

Offset: 1

Amiram Eldar, Jan 20 2023

nonn

The corresponding numbers of divisors are 1, 2, 4, 6, 8, 9, 12, 18, 20, 24, ... .

This sequence if infinite since there are refactorable numbers with arbitrarily large number of divisors. E.g., for any prime p, p^(p-1) is a refactorable number with p divisors.

Amiram Eldar, Table of n, a(n) for n = 1..60

Subsequence of A033950.
Cf. A000005, A073904, A110821.
Similar sequences: A002182, A335317, A356078, A359963.

seq[nmax_] := Module[{s = {}, dm = 0, d}, Do[d = DivisorSigma[0, n]; If[d > dm && Divisible[n, d], dm = d; AppendTo[s, n]], {n, 1, nmax}]; s]; seq[10^6]

lista(nmax) = {my(dm = 0, d); for(n = 1, nmax, d = numdiv(n); if(d > dm && n%d == 0, dm = d; print1(n, ", "))); }

cp's OEIS Frontend

A359964 Refactorable numbers (A033950) having more divisors than all smaller refactorable numbers.

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