|
|
A153825
|
|
Sum of proper divisors minus the number of proper divisors of n!.
|
|
2
|
|
|
0, 0, 0, 3, 29, 225, 1669, 14245, 118705, 1118001, 11705019, 144091717, 1738439017, 24817157329, 355309322689, 5378578597729, 86081749391905, 1570394279028289, 28281459220178401, 572031558109560385, 11458497230555053681
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,4
|
|
COMMENTS
|
a(n) is the sum of proper divisors minus the number of proper divisors of factorial number A000142(n).
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
with(numtheory): seq(sigma(factorial(n))-factorial(n)-tau(factorial(n))+1, n = 0 .. 22); # Emeric Deutsch, Jan 07 2009
|
|
MATHEMATICA
|
Table[DivisorSigma[1, n!]-n!-(DivisorSigma[0, n!]-1), {n, 0, 20}] (* Harvey P. Dale, Jan 14 2012 *)
|
|
PROG
|
(Magma) [DivisorSigma(1, Factorial(n)) - Factorial(n) - (DivisorSigma(0, Factorial(n))-1): n in [0..20]]; // Vincenzo Librandi, Aug 31 2016
(PARI) a(n) = (sigma(n!) - n!) - (numdiv(n!) - 1); \\ Michel Marcus, Aug 31 2016
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|