

A158661


Least number k such that sigma_n(k) > sigma_n(k+1), where sigma_n(k) = sum of the nth powers of the divisors of k.


0



4, 4, 6, 24, 60, 144, 360, 852, 1968, 4488, 10068, 22272, 48780, 105948, 228588, 490404, 1046976, 2225964, 4715400, 9956976, 20965212, 44031360, 92262348, 192920784, 402629256, 838827576, 1744784388, 3623814864, 7516104564
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OFFSET

0,1


COMMENTS

It appears that the inequality a(n+1) > (2+2/n)*a(n) is true for n > 4.


LINKS

Table of n, a(n) for n=0..28.


FORMULA

For n>0, a(n) = A098475(n)  1.


EXAMPLE

The values of the sigma_3 function (A001158) are increasing up to 25. Hence a(3)=24.


MATHEMATICA

Join[{4, 4}, Table[k=Floor[NSolve[Zeta[n](x1)^n==x^n, x, WorkingPrecision>100][[ 1, 1, 2]]]; While[DivisorSigma[n, k]<DivisorSigma[n, k+1], k++ ]; k, {n, 2, 30}]]


CROSSREFS

Sequence in context: A128089 A019176 A143391 * A264578 A261146 A090531
Adjacent sequences: A158658 A158659 A158660 * A158662 A158663 A158664


KEYWORD

nonn


AUTHOR

T. D. Noe, Mar 23 2009


STATUS

approved



