OFFSET
1,2
COMMENTS
a(n) is the smallest m such that A047994(m)=n, or -1 if this m does not exist. Proof of nonexistence may be done by transversing all A045778(n) factorizations of n, increasing each factor in these factorizations by 1 and showing that none of these modified products is a product of powers of distinct primes.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
a[n_] := Module[{v = invUPhi[n]}, If[v == {}, -1, v[[1]]]]; Array[a, 100] (* Amiram Eldar, Apr 01 2023, using the function invUPhi from A361966 *)
CROSSREFS
KEYWORD
sign
AUTHOR
R. J. Mathar, Dec 07 2007
STATUS
approved