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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064804 Numbers 2*k such that phi(2*k + 2) < phi(2*k). 1

%I #14 Jul 28 2023 21:40:14

%S 16,22,28,34,38,40,46,52,58,64,68,76,82,86,88,94,98,100,106,112,118,

%T 124,128,130,134,136,142,148,152,154,158,160,166,172,178,184,188,190,

%U 194,196,202,206,208,214,218,220,226,232,236,238,244,248,250,256,262,268

%N Numbers 2*k such that phi(2*k + 2) < phi(2*k).

%H Harry J. Smith, <a href="/A064804/b064804.txt">Table of n, a(n) for n = 1..1000</a>

%t 2Select[ Range[200], EulerPhi[2# + 2] < EulerPhi[2# ] & ]

%o (PARI) { n=e=0; forstep (m=2, 10^9, 2, f=eulerphi(m); if (f<e, write("b064804.txt", n++, " ", m - 2); if (n==1000, return)); e=f ) } \\ _Harry J. Smith_, Sep 26 2009

%Y Cf. A001837.

%K easy,nonn

%O 1,1

%A _Robert G. Wilson v_, Oct 21 2001

%E a(41)-a(56) from _Harry J. Smith_, Sep 26 2009

%E Name clarified by _Sean A. Irvine_, Jul 28 2023

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 18:16 EDT 2024. Contains 371916 sequences. (Running on oeis4.)