A360780 Least refactorable number > n.

1, 2, 8, 8, 8, 8, 8, 8, 9, 12, 12, 12, 18, 18, 18, 18, 18, 18, 24, 24, 24, 24, 24, 24, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 40, 40, 40, 40, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 60, 60, 60, 60, 72, 72, 72, 72, 72, 72, 72, 72, 72

Offset

0,2

Comments

"next refactorable number" function.

Links

Table of n, a(n) for n=0..68.

Example

a(0) = 1 because the least refactorable number > 0 is 1.
a(1) = 2 because the least refactorable number > 1 is 2.
a(2) = 8 because the least refactorable number > 2 is 8.

Mathematica

a[n_] := Module[{m = n + 1}, While[! Divisible[m, DivisorSigma[0, m]], m++]; m]; a[0] = 1; Array[a, 100, 0] (* Amiram Eldar, Feb 20 2023 *)

Prog

(PARI) a(n) = my(k=n+1); while (k % numdiv(k), k++); k; \\ Michel Marcus, Feb 20 2023

Crossrefs

Cf. A033950.

Sequence in context: A256849 A138300 A137575 * A183393 A284781 A289841

Adjacent sequences: A360777 A360778 A360779 * A360781 A360782 A360783

Keyword

nonn

Author

Ctibor O. Zizka, Feb 20 2023

Status

approved