OFFSET
1,1
COMMENTS
Primes {2,5,7} are units in carryless digital root arithmetic in base 10.
Composites which are also primes in carryless digital root arithmetic in base 10 begin {6, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, ...}.
1 is a unit and also a unit in carryless digital root arithmetic in base 10.
What is the asymptotic density of this sequence?
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Jul 17 2010
STATUS
approved