|
%I #22 Apr 16 2023 10:42:46
%S 10,16,18,22,37,54,66,93,142,150,246,294,405,457,618,630,774,803,1013,
%T 1026,1110,1146,1254,1272,1297,1458,1590,1686,1822,1830,2032,2166,
%U 2454,2625,2646,2662,2694,2934,3030,3218,3323,3510,3990,4266,4342,4374,4614,4806,4854,4950,5182,5286
%N Numbers n such that phi(n-2)=phi(n+2) where phi=A000010.
%F a(n) = A179186(n)+2. - _R. J. Mathar_, Jun 26 2011
%t Select[Range[3, 5000], EulerPhi[# - 2] == EulerPhi[# + 2] &] (* _Alonso del Arte_, Jun 28 2011 *)
%t Flatten[Position[Partition[EulerPhi[Range[5300]],5,1],_?(#[[1]] == #[[5]]&), 1,Heads -> False]]+2 (* _Harvey P. Dale_, Jul 01 2019 *)
%o (PARI) for(n=3,1e4,if(eulerphi(n-2)==eulerphi(n+2),print1(n", "))) \\ _Charles R Greathouse IV_, Jun 27 2011
%Y Cf. A000010, A066812.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Jun 26 2011
|
