A152615 Numbers k such that exactly two subsets of proper divisors of k sum to k.

12, 18, 42, 56, 66, 100, 176, 196, 208, 348, 372, 444, 460, 492, 516, 550, 564, 580, 636, 708, 732, 736, 738, 774, 804, 812, 820, 846, 852, 868, 876, 928, 948, 954, 968, 992, 996, 1036, 1062, 1068, 1098, 1148, 1164, 1204, 1206, 1212, 1236, 1278, 1284, 1308

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..2500

Example

k = 12: proper divisors of 12 = {1,2,3,4,6} and 12 = 2 + 4 + 6 = 1 + 2 + 3 + 6.

Mathematica

spdQ[n_]:=Module[{pds=Most[Divisors[n]]}, Length[Select[Subsets[ pds, Length[ pds]], Total[#] == n&]]==2]; Select[Range[1400], spdQ] (* Harvey P. Dale, Jan 23 2015 *)

Crossrefs

Cf. A064771, A065205, A065235.

Sequence in context: A124205 A338259 A133403 * A258088 A259263 A341039

Adjacent sequences: A152612 A152613 A152614 * A152616 A152617 A152618

Keyword

nonn

Author

Zak Seidov, Oct 29 2009

Status

approved