A225354 Numbers that can be written as sum of distinct squarefree divisors.

1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 82, 83, 84, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 102

Offset

1,2

Comments

A225245(a(n)) > 0.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Mathematica

f[n_] := f[n] = Coefficient[Product[If[MoebiusMu[d] != 0, 1 + x^d, 1], {d, Divisors[n]}], x, n];
ParallelTable[If[f[k] > 0, k, Nothing], {k, 1, 1000}] (* Jean-François Alcover, May 04 2024, after Ilya Gutkovskiy in A225245 *)

Prog

(Haskell)
import Data.List (findIndices)
a225354 n = a225354_list !! (n-1)
a225354_list = map (+ 1) $ findIndices (> 0) a225245_list

Crossrefs

Cf. A225353 (complement).

Sequence in context: A349810 A317092 A349019 * A166111 A004762 A061854

Adjacent sequences: A225351 A225352 A225353 * A225355 A225356 A225357

Keyword

nonn

Author

Reinhard Zumkeller, May 05 2013

Status

approved