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A099633 Numbers n such that (phi[n-2]+phi[n+2])/2 = phi[n]. 2-phi/balanced numbers. See also A066167. 1
2, 5, 10, 14, 20, 25, 50, 80, 154, 200, 434, 520, 610, 815, 1205, 1345, 2680, 3200, 3560, 4669, 7330, 9290, 10130, 11705, 17630, 24410, 25090, 33385, 34205, 39754, 39785, 40870, 48470, 55979, 59090, 73165, 75470, 78035, 95990, 107680, 115685, 120230 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..500

EXAMPLE

n=154,phi[152]=72,phi[156]=48,phi[154]=60

MATHEMATICA

Flatten[Position[Partition[EulerPhi[Range[0, 121000]], 5, 1], _?((#[[1]]+ #[[5]]) /2 == #[[3]]&), {1}, Heads->False]]+1 (* Harvey P. Dale, Jan 20 2015 *)

CROSSREFS

Cf. A066167, A000010, A099631, A099632.

Sequence in context: A331605 A115757 A159032 * A082745 A064955 A101725

Adjacent sequences:  A099630 A099631 A099632 * A099634 A099635 A099636

KEYWORD

nonn

AUTHOR

Labos Elemer, Oct 27 2004

STATUS

approved

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Last modified October 31 00:25 EDT 2020. Contains 338095 sequences. (Running on oeis4.)