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A064374

Numbers k such that sigma(k) > phi(k)^2.

2, 4, 6, 10, 12, 18, 30

OFFSET

1,1

COMMENTS

Also numbers k such that sigma(k) > tau(k)*phi(k). - Benoit Cloitre, Aug 06 2002

There are no further terms. - Benoit Cloitre, Aug 06 2002

LINKS

FORMULA

Solutions to A000203(k) > A000010(k)^2.

EXAMPLE

k = {2, 4, 6, 10, 12, 18, 30};

sigma(k) = {3, 7, 12, 18, 28, 39, 72};

phi(k) = {1, 2, 2, 4, 4, 6, 8};

phi(k)^2 = {1, 4, 4, 16, 16, 36, 64};

sigma(k) - phi(k)^2 = {2, 3, 8, 2, 12, 3, 8}.

No more solutions below 10000000.

MATHEMATICA

Select[Range[30], DivisorSigma[1, #]>EulerPhi[#]^2&] (* Harvey P. Dale, Sep 27 2024 *)

CROSSREFS

KEYWORD

nonn,fini,full

AUTHOR

Labos Elemer, Sep 27 2001

STATUS

approved

URL: https://oeis.org/A064374