A175431 Numbers m such that sigma(m) is not a nontrivial power, i.e., sigma(m) = A000203(n) is not equal a^b where a and b are greater than 1.

1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79

Offset: 1

Author

Jaroslav Krizek, May 10 2010

Keywords

• nonn

Comments

Complement of A065496.

A175432(a(n)) = 1 for n >= 1.

Examples

			Number 3 is not in the sequence because sigma(3) = 4 = 2^2.
		

Crossrefs

Cf. A000203, A065496, A175432.

Extensions

Extended by Ray Chandler, Aug 20 2010