A095113 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).

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, 41, 36, 46, 29, 66, 32, 49, 47, 54, 48, 78, 38, 60, 55, 68, 42, 91, 43, 70, 69, 72, 48, 103, 57, 87, 72, 82, 53, 112, 72, 92, 80, 89, 59, 138, 61, 95, 93, 98, 83, 139, 67, 109, 96, 132

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Example

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.

Mathematica

a[1]=1; a[n_]:=a[n]=Module[{as=a/@Range[n-1]}, Plus@@(If[MemberQ[as, # ], n/#, 0]& /@ Divisors[n])]
Fold[Append[#1, Total[#2/Intersection[Divisors[#2], #1]]] &, {1}, Range[2, 70]] (* Ivan Neretin, Jun 20 2019 *)

Crossrefs

Sequence in context: A232929 A001634 A172989 * A345179 A367584 A002517

Adjacent sequences: A095110 A095111 A095112 * A095114 A095115 A095116

Keyword

nonn

Author

Dean Hickerson, following a suggestion of Leroy Quet, May 28 2004

Status

approved