cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A064805 Numbers k such that phi(k) > phi(k+2).

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%I A064805 #13 Jun 18 2022 19:10:56
%S A064805 13,16,19,22,23,25,28,31,34,37,38,40,43,46,47,49,52,53,55,58,61,64,67,
%T A064805 68,73,76,79,82,83,85,86,88,89,91,94,97,98,100,103,106,109,112,113,
%U A064805 115,118,121,124,127,128,130,131,133,134,136,139,142,143,145,148,151,152
%N A064805 Numbers k such that phi(k) > phi(k+2).
%H A064805 Harry J. Smith, <a href="/A064805/b064805.txt">Table of n, a(n) for n = 1..1000</a>
%t A064805 Select[ Range[150], EulerPhi[ # ] > EulerPhi[ #+2 ] & ]
%t A064805 Position[Partition[EulerPhi[Range[200]],3,1],_?(First[#]>Last[#]&), 1, Heads->False]//Flatten (* _Harvey P. Dale_, Jun 14 2017 *)
%o A064805 (PARI) { n=0; for (m=1, 10^9, f=eulerphi(m); if (eulerphi(m)>eulerphi(m + 2), write("b064805.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Sep 26 2009
%Y A064805 Cf. A000010 (phi), A001837.
%K A064805 easy,nonn
%O A064805 1,1
%A A064805 _Robert G. Wilson v_, Oct 21 2001
%E A064805 a(60)-a(61) from _Harry J. Smith_, Sep 26 2009