A161751 Digital root of Abelian numbers (A051532).

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, 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

Offset: 1

Author

Parthasarathy Nambi, Jun 17 2009

Keywords

• nonn
• base

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

Examples

			161 is an Abelian number whose digital root is 8.
		

Crossrefs

Cf. A051532.