A333262 -id:A333262 - cp's OEIS frontend

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

Amiram Eldar, Mar 13 2020

nonn

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

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

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

Cf. A071324, A333262.

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

A333263 Numbers k such that the sum of iterations of the alternating sum of divisors function A071324 starting from k is equal to 2*k.

Original entry on oeis.org

5, 447, 700, 3122, 20649, 25816, 70221, 205701, 408624, 2574176, 3827656, 4753563, 12129928, 118200807

Offset: 1

Amiram Eldar, Mar 13 2020

			5 is a term since the iterations of A071324 with a starting value of 5 give A071324(5) = 4, A071324(4) = 3, A071324(3) = 2, and A071324(2) = 1, whose sum is 4 + 3 + 2 + 1 = 10 = 2 * 5.

Cf. A071324, A331017, A333262.

f[n_] := Plus @@ (-(d = Divisors[n])*(-1)^(Range[Length[d],1,-1])); seqQ[n_]:=Plus @@ FixedPointList[f,n] == 3n + 1; Select[Range[10000], seqQ]

cp's OEIS Frontend

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

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica