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 A115918 Numbers k such that sigma(k) - phi(k) 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: A351183 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 October 1 17:40 EDT 2023. Contains 365828 sequences. (Running on oeis4.)