OFFSET
1,3
COMMENTS
For n > 1, a(n) gives the unique solution k of d(m^k) = m where d = A000005. For m = 1, any integer k will do, we choose the smallest positive solution a(1) = 1.
For prime p, p-1 is in this sequence.
For odd semiprime s, (s-1)/2 is in this sequence.
LINKS
David W. Wilson, Table of n, a(n) for n=1..10000
EXAMPLE
MATHEMATICA
f[n_] := Module[{e = FactorInteger[n][[;; , 2]], k = 1}, While[n > Times @@ (k*e + 1), k++]; If[n == Times @@ (k*e + 1), k, Nothing]]; f[1] = 1; Array[f, 250] (* Amiram Eldar, Apr 09 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
David W. Wilson, Sep 26 2010
STATUS
approved