A120360 Even refactorable numbers k such that the number of odd divisors of k and the number of even divisors of k are both even divisors of k.
12, 24, 80, 180, 240, 252, 360, 396, 468, 480, 504, 560, 612, 684, 720, 792, 828, 880, 896, 936, 972, 1040, 1044, 1116, 1200, 1224, 1332, 1344, 1360, 1368, 1440, 1476, 1520, 1548, 1620, 1656, 1692, 1840, 1908, 1944, 2000, 2088, 2124, 2196, 2232, 2320
Offset: 1
Keywords
Examples
a(1) = 12 since r = 2, s = 4, t = r + s = 6.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
-
Mathematica
oddtau[n_] := DivisorSigma[0, n/2^IntegerExponent[n, 2]]; seqQ[n_] := Module[{d = DivisorSigma[0, n], o = odd[n]}, EvenQ[d] && EvenQ[o] && Divisible[n, d] && Divisible[n, o] && Divisible[n, d - o]]; Select[Range[2, 2320, 2], seqQ] (* Amiram Eldar, Jan 15 2020 *)
Comments