OFFSET
1,3
COMMENTS
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Unitary Divisor.
FORMULA
EXAMPLE
As the unitary divisors of 12 are 1, 3, 4 and 12, which sum to 20, then a(12) = 20 - 2*12 = -4.
MAPLE
A129468 := proc(n)
A034448(n)-2*n ;
end proc:
seq(A129468(n), n=1..40) ; # R. J. Mathar, Nov 10 2014
MATHEMATICA
UnitaryDivisors[n_Integer?Positive] := Select[Divisors[n], GCD[ #, n/# ] == 1&]; sstar[n_] := Plus@@UnitaryDivisors[n] - n; sstar[ # ] - # &/@ Range[40]
a[n_] := Times @@ (1 + Power @@@ FactorInteger[n]) - 2*n; a[1] = -1; Array[a, 100] (* Amiram Eldar, Apr 06 2024 *)
PROG
(PARI) a(n) = {my(f = factor(n)); prod(i=1, #f~, 1 + f[i, 1]^f[i, 2]) - 2*n; } \\ Amiram Eldar, Apr 06 2024
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Ant King, Apr 17 2007
STATUS
approved