A095113 - OEIS

%I #13 Jun 20 2019 16:26:14

%S 1,2,3,6,5,12,7,12,12,17,11,25,13,23,23,24,18,37,19,34,31,35,24,51,31,

%T 41,36,46,29,66,32,49,47,54,48,78,38,60,55,68,42,91,43,70,69,72,48,

%U 103,57,87,72,82,53,112,72,92,80,89,59,138,61,95,93,98,83,139,67,109,96,132

%N a(1)=1. a(n) is the sum of n/d over all divisors d of n which are among a(1), ..., a(n-1).

%H Ivan Neretin, <a href="/A095113/b095113.txt">Table of n, a(n) for n = 1..10000</a>

%e The divisors of 8 are 1, 2, 4 and 8, of which only 1 and 2 occur among a(1), ..., a(7), so a(8) = 8/1 + 8/2 = 12.

%t a[1]=1; a[n_]:=a[n]=Module[{as=a/@Range[n-1]}, Plus@@(If[MemberQ[as, # ], n/#, 0]& /@ Divisors[n])]

%t Fold[Append[#1, Total[#2/Intersection[Divisors[#2], #1]]] &, {1}, Range[2, 70]] (* _Ivan Neretin_, Jun 20 2019 *)

%K nonn

%O 1,2

%A _Dean Hickerson_, following a suggestion of _Leroy Quet_, May 28 2004