A081761 Least number >n having same type of prime factorization, a(1)=1.

1, 3, 5, 9, 7, 10, 11, 27, 25, 14, 13, 18, 17, 15, 21, 81, 19, 20, 23, 28, 22, 26, 29, 40, 49, 33, 125, 44, 31, 42, 37, 243, 34, 35, 38, 100, 41, 39, 46, 54, 43, 66, 47, 45, 50, 51, 53, 80, 121, 52, 55, 63, 59, 56, 57, 88, 58, 62, 61, 84, 67, 65, 68, 729, 69, 70, 71, 75, 74, 78

Offset: 1

Author

Reinhard Zumkeller, Apr 09 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A046523, A085072.

Programs

Mathematica

sig[n_] := Sort @ FactorInteger[n][[;; , 2]]; a[1] = 1; a[n_] := Module[{sign = sig[n], k = n + 1}, While[sig[k] != sign, k++]; k]; Array[a, 70] (* Amiram Eldar, Dec 26 2020 *)

PARI

a(n) = {if (n==1, 1, my(k=1, s = vecsort(factor(n)[,2]~)); while (vecsort(factor(n+k)[,2]~) != s, k++); n+k;)} \\ Michel Marcus, Nov 02 2020

Formula

A046523(a(n)) = A046523(n).

a(n) = n + A085072(n). - Amiram Eldar, Dec 26 2020