OFFSET
1,1
COMMENTS
Observe that the values giving stationary value in 6 steps are rather large.
"d" in the definition refers to the number of divisors of n. - Harvey P. Dale, Mar 06 2015
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
A036459(a(n)) = 6. - Ivan Neretin, Jan 25 2016
EXAMPLE
a(1)=5040 and the nested d functions are 60,12,6,4,3 and the 6th is 2. a(5)=10080 and iterating d with 10080 initial value, after 6 iterations the convergence takes place through 72,12,6,4,3 transients, i.e., 2 is reached on the 6th step.
MATHEMATICA
draQ[n_]:=Length[FixedPointList[DivisorSigma[0, #]&, n, 7]]==8; Select[ Range[ 21000], draQ] (* Harvey P. Dale, Mar 06 2015 *)
PROG
(PARI) is(n)=for(i=1, 5, n=numdiv(n); if(n<3, return(0))); numdiv(n)==2 \\ Charles R Greathouse IV, Sep 17 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved