A098475 a(n) is the smallest integer k for which sigma_n(k) <= sigma_n(k-1) where sigma_n(k) = sum of the n-th powers of the divisors of k.

3, 5, 7, 25, 61, 145, 361, 853, 1969, 4489, 10069, 22273, 48781, 105949, 228589, 490405, 1046977, 2225965, 4715401, 9956977, 20965213, 44031361, 92262349, 192920785, 402629257, 838827577, 1744784389, 3623814865, 7516104565

Offset: 0

Author

John L. Drost, Oct 26 2004

Keywords

• nonn

Comments

a(n) has to be larger than the solution to Zeta(n)*(x-1)^n=x^n.

Examples

			a(1)=5 since sigma(1)=1,sigma(2)=3,sigma(3)=4, sigma(4)=7, but sigma(5)=6.
		

Programs

PARI

a(n) = {my(k = 2); while(sigma(k, n) > sigma(k-1, n), k++); k;} \\ Michel Marcus, Aug 18 2013