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

1,2

Comments

Similar to A270875 but also counts singletons, the trivial solutions.

Links

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..200

Formula

a(n) = A270875(n) + n.

Mathematica

Table[Length@ Select[Rest@ Subsets@ Range@ n, Total@ # == LCM @@ # &], {n, 22}] (* Michael De Vlieger, Mar 27 2016 *)

Prog

(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; }

Crossrefs

Cf. A084422, A270875.

Sequence in context: A189404 A316681 A161793 * A188092 A188080 A048262

Adjacent sequences: A270967 A270968 A270969 * A270971 A270972 A270973

Keyword

nonn

Author

Michel Marcus, Mar 27 2016

Extensions

a(31)-a(58) from Hiroaki Yamanouchi, Mar 30 2016

Status

approved