A270970 Number of subsets of {1,...,n} with sum of elements equal to least common multiple of elements.
1, 2, 4, 5, 6, 8, 9, 11, 14, 16, 17, 21, 22, 24, 28, 31, 32, 37, 38, 53, 56, 57, 58, 71, 72, 73, 77, 85, 86, 131, 132, 138, 141, 142, 143, 163, 164, 165, 167, 289, 290, 310, 311, 316, 403, 404, 405, 454, 455, 458, 460, 463, 464, 478, 479, 557, 559, 560, 561
Offset: 1
Keywords
Links
- Hiroaki Yamanouchi, Table of n, a(n) for n = 1..200
Programs
-
Mathematica
Table[Length@ Select[Rest@ Subsets@ Range@ n, Total@ # == LCM @@ # &], {n, 22}] (* Michael De Vlieger, Mar 27 2016 *) -
PARI
a(n) = {nb = 0; S = vector(n, k, k); for (i = 0, 2^n - 1, ss = vecextract(S, i); if (sum(k=1, #ss, ss[k]) == lcm(ss), nb++);); nb;}
Formula
a(n) = A270875(n) + n.
Extensions
a(31)-a(58) from Hiroaki Yamanouchi, Mar 30 2016
Comments