|
| |
|
|
A173557
|
|
a(n)=Product{p-1| p is prime and divisor of n}
|
|
7
|
|
|
|
1, 1, 2, 1, 4, 2, 6, 1, 2, 4, 10, 2, 12, 6, 8, 1, 16, 2, 18, 4, 12, 10, 22, 2, 4, 12, 2, 6, 28, 8, 30, 1, 20, 16, 24, 2, 36, 18, 24, 4, 40, 12, 42, 10, 8, 22, 46, 2, 6, 4, 32, 12, 52, 2, 40, 6, 36, 28, 58, 8, 60, 30, 12, 1, 48, 20, 66, 16, 44, 24, 70, 2, 72, 36, 8, 18, 60, 24, 78, 4, 2, 40, 82, 12
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,3
|
|
|
LINKS
|
Table of n, a(n) for n=1..84.
|
|
|
FORMULA
|
a(n) = A003958(n) iff n is squarefree. a(n)= Abs(A023900(n)).
Multiplicative with a(p^e) = p-1, e>=1. - R. J. Mathar, Mar 30 2011
a(n) = phi(rad(n)) = A000010(A007947(n)). - Enrique Pérez Herrero, May 30 2012
a(n) = A000010(n) / A003557(n). - Jason Kimberley, Dec 09 2012
|
|
|
EXAMPLE
|
300=3*5^2*2^2 ==> a(300)=(3-1)*(2-1)*(5-1)=8
|
|
|
MAPLE
|
A173557 := proc(n) local dvs; dvs := numtheory[factorset](n) ; mul(d-1, d=dvs) ; end proc: # R. J. Mathar, Feb 02 2011
|
|
|
MATHEMATICA
|
a[n_] := Module[{fac = FactorInteger[n]}, Product[fac[[i, 1]]-1, {i, Length[fac]}]]; Table[a[n], {n, 300}]
|
|
|
CROSSREFS
|
Cf. A141564.
Sequence in context: A070777 A173614 A023900 * A141564 A046791 A187203
Adjacent sequences: A173554 A173555 A173556 * A173558 A173559 A173560
|
|
|
KEYWORD
|
nonn,easy,mult
|
|
|
AUTHOR
|
José María Grau Ribas, Feb 21 2010
|
|
|
STATUS
|
approved
|
| |
|
|
