The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A076773 2-nadirs of phi: numbers k such that phi(k-2) > phi(k-1) > phi(k) < phi(k+1) < phi(k+2). 3
 315, 525, 735, 1155, 1365, 1575, 1755, 1785, 1815, 1995, 2145, 2415, 2475, 2805, 3045, 3315, 3465, 3885, 4095, 4125, 4305, 4515, 4725, 4935, 5115, 5145, 5355, 5775, 6045, 6195, 6405, 6435, 6615, 6825, 7035, 7095, 7245, 7395, 7455, 7605, 7665, 8085 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS I call n a "k-nadir" (or nadir of depth k) of the arithmetical function f if n satisfies f(n-k) > ... > f(n-1) > f(n) < f(n+1) < ... < f(n+k). If just phi(n-1) > phi(n) < phi(n+1) is required for odd n, does this lead to a different sequence? That is, are there consecutive odd numbers in A161962 or consecutive even numbers in A161963? - Jianing Song, Jan 12 2019 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..5000 from G. C. Greubel) EXAMPLE phi(313), ..., phi(317) equal 312, 156, 144, 156, 316, respectively, so 315 is a 2-nadir of phi(n). MATHEMATICA Select[Range[3, 10^4], EulerPhi[#-2] > EulerPhi[#-1] > EulerPhi[#] < EulerPhi[#+1] < EulerPhi[#+2] &] PROG (Sage) [n for n in (3..9000) if euler_phi(n-2) > euler_phi(n-1) > euler_phi(n) < euler_phi(n+1) < euler_phi(n+2)] # G. C. Greubel, Feb 27 2019 (Magma) eu:=EulerPhi; f:=func; f1:= func; [k:k in [3..8100]|f(k) and f1(k)]; // Marius A. Burtea, Feb 19 2020 CROSSREFS Cf. A000010, A161962, A161963. Sequence in context: A295990 A349868 A349937 * A114807 A109130 A284981 Adjacent sequences: A076770 A076771 A076772 * A076774 A076775 A076776 KEYWORD nonn AUTHOR Joseph L. Pe, Nov 14 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 21 02:47 EDT 2023. Contains 365486 sequences. (Running on oeis4.)