OFFSET
0,4
COMMENTS
a(n) is the sum of proper divisors minus the number of proper divisors of factorial number A000142(n).
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..500
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
Omar E. Pol, Jan 02 2009
EXTENSIONS
Extended by Emeric Deutsch, Jan 07 2009
STATUS
approved