OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
Number 6859 with divisors 1, 19, 361, 6859 is in sequence because all divisors have additive digital root of 1.
MAPLE
filter:= n -> not isprime(n) and numtheory:-factorset(n) mod 9 = {1}:
filter(1):= true:
select(filter, [seq(i, i=1..20000, 9)]); # Robert Israel, May 10 2020
MATHEMATICA
(* First run the program for A211821 *) Select[A211821, Not[PrimeQ[#]] &] (* Alonso del Arte, May 02 2012 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Apr 26 2012
STATUS
approved