|
%I #22 Apr 06 2020 11:37:50
%S 3,5,20,156,254,377,593,1800,5903,5981,7925,18669,19240,41274,48296,
%T 135700,146866,228028,234303,251216,407377,654288,802222,886223,
%U 938654,1063412,1072766,1212140,1238668,1515063,1609346,2080991,2097725,2363130,2408674,2916514
%N Integers k such that phi(prime(k)+1) = phi(prime(k)-1).
%C Integers k such that A008331(k) = A008330(k).
%H Giovanni Resta, <a href="/A066902/b066902.txt">Table of n, a(n) for n = 1..675</a>
%F a(n) = primepi(A067890(n)). - _Giovanni Resta_, Apr 06 2020
%t Select[Range[1000000],EulerPhi[Prime[#]-1]==EulerPhi[Prime[#]+1]&] (* _Harvey P. Dale_, Feb 25 2012 *)
%o (PARI) isok(k) = my(p=prime(k)); eulerphi(p+1) == eulerphi(p-1); \\ _Michel Marcus_, Apr 06 2020
%Y Cf. A000010, A008864, A006093, A008330, A008331, A067890.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Jan 26 2002
%E More terms from _Harvey P. Dale_, Feb 25 2012
%E More terms from _Jinyuan Wang_, Apr 05 2020
|
