A220160 Numbers n for which phi(n) = phi(n-1) - phi(n+1).

194, 3530, 9338, 27230, 46794, 78182, 90194, 112994, 135014, 437184, 849404, 935220, 1078580, 1283600, 1986974, 2209584, 2341184, 2411174, 2689694, 2744144, 3619070, 3712544, 4738184, 5132984, 6596120, 7829030, 8184714, 12176108, 12292004, 13342958, 26400842

Offset

1,1

Links

Donovan Johnson, Table of n, a(n) for n = 1..100

Example

phi(3529) - phi(3531) = 3528 - 2120 = 1408 = phi(3530).

Mathematica

Select[Range[10^6], EulerPhi[#] == EulerPhi[# - 1] - EulerPhi[# + 1] &]
With[{ep=EulerPhi[Range[27500000]]}, Flatten[Position[Partition[ ep, 3, 1], _?(#[[1]]- #[[3]]==#[[2]]&), {1}, Heads->False]]]+1 (* Harvey P. Dale, Feb 04 2015 *)

Crossrefs

Cf. A000010, A076529.

Sequence in context: A205621 A205356 A281807 * A333875 A183583 A296893

Adjacent sequences: A220157 A220158 A220159 * A220161 A220162 A220163

Keyword

nonn

Author

Carl Najafi, Dec 06 2012

Status

approved