OFFSET
1,4
COMMENTS
For given n, iterate a(n); a(a(n)); a(a(a(n))); ... Does this iterative process always lead to a(a(...(a(n))...) = 1? - Ctibor O. Zizka, Apr 17 2008
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = Sum_{i=1..tau(n)} (tau(n)-i)*d_i, where {d_i}, i=1..tau(n), is increasing sequence of divisors of n.
EXAMPLE
a(6) = dot_product(3,2,1,0)*(1,2,3,6) = 3*1 + 2*2 + 1*3 + 0*6 = 10.
MAPLE
with(numtheory): seq(add((tau(n)-i)*sort(convert(divisors(n), 'list'))[i], i=1..tau(n)), n=1..200);
PROG
(PARI) { for (n=1, 1000, d=divisors(n); t=length(d); a=sum(i=1, t - 1, (t - i)*d[i]); write("b064947.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 01 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Oct 28 2001
STATUS
approved