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A078776 Numbers k such that phi(k-1) < phi(k) < phi(k+1), where phi is the Euler totient function (A000010). 4
106, 166, 316, 526, 586, 736, 1156, 1366, 1485, 1486, 1576, 1756, 1786, 1816, 1996, 2146, 2206, 2416, 2476, 2535, 2536, 2806, 2836, 3003, 3004, 3046, 3316, 3466, 3675, 3676, 3886, 3927, 3928, 4096, 4126, 4306, 4455, 4456, 4485, 4486, 4516, 4726, 4785, 4786 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

Jean-Marie De Koninck, Those Fascinating Numbers, American Mathematical Society, 2009, page 34, entry 105.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harvey P. Dale)

EXAMPLE

phi(105)=48 < phi(106)=52 < phi(107)=106, so 106 is in the sequence.

MATHEMATICA

Flatten[Position[Partition[EulerPhi[Range[5000]], 3, 1], _?(Min[Differences[ #]]> 0&)]//Quiet]+1 (* Harvey P. Dale, Jun 14 2019 *)

PROG

(PARI) for (n=2, 3000, if (eulerphi(n-1)<eulerphi(n) && eulerphi(n)<eulerphi(n+1), print1(n", ")))

CROSSREFS

Cf. A000010.

Sequence in context: A070796 A045093 A304978 * A188006 A160725 A044338

Adjacent sequences:  A078773 A078774 A078775 * A078777 A078778 A078779

KEYWORD

nonn

AUTHOR

Jon Perry, Jan 09 2003

EXTENSIONS

More terms from Michel Marcus, Mar 17 2014

STATUS

approved

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Last modified January 25 04:21 EST 2022. Contains 350565 sequences. (Running on oeis4.)