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A115918 Numbers n such that sigma(n)-phi(n) is a 4th power. 1
1, 15, 560, 570, 1071, 1102, 1185, 2035, 2071, 2128, 2185, 3007, 3215, 4087, 4487, 4584, 5406, 9204, 10727, 13912, 16675, 17951, 17970, 19127, 20553, 24288, 24887, 28247, 28290, 30216, 34951, 35807, 35985, 38551, 40967, 44472, 44951, 55247 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..340

EXAMPLE

sigma(16675)-phi(16675)=10000=10^4.

MATHEMATICA

fpQ[n_]:=IntegerQ[(DivisorSigma[1, n]-EulerPhi[n])^(1/4)]; Select[Range[ 60000], fpQ] (* Harvey P. Dale, Jun 28 2012 *)

CROSSREFS

Cf. A056917, A062385.

Sequence in context: A171197 A061174 A255956 * A110840 A012178 A012229

Adjacent sequences:  A115915 A115916 A115917 * A115919 A115920 A115921

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 06 2006

STATUS

approved

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Last modified August 12 05:33 EDT 2020. Contains 336438 sequences. (Running on oeis4.)