OFFSET
1,2
COMMENTS
The terms of A203897 having all divisors in A020449 (in particular, the first 1022 terms) are a subsequence. - M. F. Hasler, May 02 2022
Since 1 and the term itself are divisors, one must only check repdigits and those containing only 1 and another digit. - Michael S. Branicky, May 02 2022
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000 (terms 1..500 from M. F. Hasler)
FORMULA
A095048(a(n)) <= 2.
MATHEMATICA
Select[Range[12000], Length[Union[Flatten[IntegerDigits/@Divisors[#]]]]<3&] (* Harvey P. Dale, May 03 2022 *)
PROG
(Python)
from sympy import divisors
def ok(n):
digits_used = set()
for d in divisors(n, generator=True):
digits_used |= set(str(d))
if len(digits_used) > 2: return False
return True
print([k for k in range(1, 9000) if ok(k)]) # Michael S. Branicky, May 02 2022
(PARI) select( {is_A206159(n)=#Set(concat([digits(d)|d<-divisors(n)]))<3}, [1..10^4]) \\ M. F. Hasler, May 02 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Feb 05 2012
EXTENSIONS
Terms corrected by Harvey P. Dale, May 02 2022
Edited by N. J. A. Sloane, May 02 2022
STATUS
approved