|
|
A225821
|
|
a(n) = Product_{p | p is prime and p, p-1 both divide n}.
|
|
1
|
|
|
1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 10, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 10, 1, 42, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 30, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 10, 1, 2, 1, 42
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
a(n) = n if n = 1, 2, 6, 42, 1806.
a(n) = 6 if n is of the form 2^i*3^j, i and j >= 1, so if n is a term of A033845.
a(n) = 10 if n is of the form 2^i*5^j, i >= 2 and j >= 1.
a(n) = 30 if n is of the form 2^i*3^j*5^k, i >=2, j >= 1 and k >= 1. (End)
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
fa=FactorInteger; d[m_]:= Product[If[IntegerQ[m/(fa[m][[i, 1]]-1)], fa[m][[i, 1]], 1], {i, Length@fa@m}]; Table[d[n], {n, 1, 333}]
|
|
PROG
|
(PARI) a(n)=my(f=factor(n)[, 1]); prod(i=1, #f, if(n%(f[i]-1)==0, f[i], 1)) \\ Charles R Greathouse IV, Nov 13 2013
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|