A099476 Smallest number having exactly n divisors d such that also d+2 is a divisor.

1, 3, 15, 12, 24, 60, 180, 120, 360, 720, 1260, 840, 1680, 3360, 2520, 7560, 5040, 10080, 30240, 32760, 27720, 85680, 83160, 55440, 110880, 166320, 277200, 526680, 360360, 831600, 942480, 1053360, 1801800, 720720, 3769920, 1441440, 2162160

Offset: 0

Author

Reinhard Zumkeller, Oct 18 2004

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 0..87

Crossrefs

Cf. A059267, A099475.

Programs

Mathematica

f[n_] := DivisorSum[n, Boole@Divisible[n, #+2] &]; m = 20; a = Table[0, {m}]; c = 0; n = 2; While[c < m, f1 = f[n];  If[f1 > 0 && f1 <= m && a[[f1]] == 0, c++; a[[f1]] = n]; n++]; Join[{1}, a] (* Amiram Eldar, Sep 02 2019 *)

Formula

A099475(a(n)) = n and A099475(m) <> n for m < a(n).