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A066232 Numbers n such that phi(n) = phi(n-2) - phi(n-1). 4
195, 3531, 9339, 27231, 46795, 78183, 90195, 112995, 135015, 437185, 849405, 935221, 1078581, 1283601, 1986975, 2209585, 2341185, 2411175, 2689695, 2744145, 3619071, 3712545, 4738185, 5132985, 6596121, 7829031, 8184715, 12176109 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

As in A065557, all terms listed here are odd. Problem: Prove that this holds in general.

LINKS

Harry J. Smith and Jud McCranie, Table of n, a(n) for n = 1..289 (first 55 terms from Harry J. Smith)

EXAMPLE

Phi(195) = 96 = 192-96 = phi(193)-phi(194).

MATHEMATICA

Select[Range[3, 10^6], EulerPhi[ # ] == EulerPhi[ # - 2] - EulerPhi[ # - 1] &]

PROG

(PARI) { n=0; for (m=3, 10^9, if (eulerphi(m) == eulerphi(m - 2) - eulerphi(m - 1), write("b066232.txt", n++, " ", m); if (n==100, return)) ) } \\ Harry J. Smith, Feb 07 2010

CROSSREFS

Cf. A066231, A067701.

Sequence in context: A295130 A257765 A259694 * A284960 A226105 A164130

Adjacent sequences:  A066229 A066230 A066231 * A066233 A066234 A066235

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Dec 18 2001

EXTENSIONS

a(13)-a(28) from Harry J. Smith, Feb 07 2010

STATUS

approved

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Last modified December 6 11:48 EST 2021. Contains 349563 sequences. (Running on oeis4.)