A099476 - OEIS

%I #7 Sep 02 2019 04:28:06

%S 1,3,15,12,24,60,180,120,360,720,1260,840,1680,3360,2520,7560,5040,

%T 10080,30240,32760,27720,85680,83160,55440,110880,166320,277200,

%U 526680,360360,831600,942480,1053360,1801800,720720,3769920,1441440,2162160

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

%H Amiram Eldar, <a href="/A099476/b099476.txt">Table of n, a(n) for n = 0..87</a>

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

%t 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 *)

%Y Cf. A059267, A099475.

%K nonn

%O 0,2

%A _Reinhard Zumkeller_, Oct 18 2004