A333265 Least number k that reaches 1 after n iterations of A071324.

1, 2, 3, 4, 5, 7, 9, 13, 17, 19, 29, 37, 49, 72, 73, 103, 155, 193, 277, 441, 527, 769, 1109, 1597, 2309, 2477, 4733, 6467, 8649, 12197, 16129, 23813, 36151, 48841, 74609, 106291, 146689, 224717, 312451, 405001, 615449, 777137, 1242487, 1540711, 2465129, 3401341

Offset

0,2

Comments

Least number k such that A333262(k) = n.

Links

Amiram Eldar, Table of n, a(n) for n = 0..55

Formula

a(5) = 7 since 7 is the least number that reaches 1 after 5 iterations of A071324: 7 -> 6 -> 4 -> 3 -> 2 -> 1.

Mathematica

s[n_] := Plus @@ (-(d = Divisors[n])*(-1)^(Range[Length[d], 1, -1])); numiter[n_] := Length @ FixedPointList[s, n] - 2; n = 0; seq={}; Do[If[numiter[k] == n, AppendTo[seq, k]; n++], {k, 1, 1000}]; seq

Crossrefs

Cf. A071324, A333262.

Sequence in context: A240178 A039863 A036802 * A055167 A064628 A188674

Adjacent sequences: A333262 A333263 A333264 * A333266 A333267 A333268

Keyword

nonn

Author

Amiram Eldar, Mar 13 2020

Status

approved