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%I #12 Jan 21 2022 23:31:03
%S 1,2,3,4,5,7,9,2,4,6,8,1,5,7,2,4,6,8,1,5,7,9,2,4,6,8,5,7,2,4,6,8,1,5,
%T 7,2,4,6,8,1,5,7,9,2,4,8,1,5,7,2,4,6,1,5,7,2,4,6,8,1,5,7,9,4,6,8
%N Digital root of Abelian numbers (A051532).
%C It is interesting to observe that it is difficult to find 3 as the digital root.
%C 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
%e 161 is an Abelian number whose digital root is 8.
%Y Cf. A051532.
%K nonn,base
%O 1,2
%A _Parthasarathy Nambi_, Jun 17 2009
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