OFFSET
1,2
COMMENTS
It is interesting to observe that it is difficult to find 3 as the digital root.
This is because if a term of A051532 is congruent to 3 (mod 9) all other prime power divisors of the number must be 2 (mod 3). The first few indexes n with a(n) = 3 are 3, 99, 131, 164, 211, 261, 293, 327, 351, 424, 450, 482, 491, .... - Charles R Greathouse IV, Feb 13 2011
EXAMPLE
161 is an Abelian number whose digital root is 8.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Jun 17 2009
STATUS
approved