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%I #8 Jan 16 2024 19:31:47
%S 1,2,3,4,6,11,19,22,27,38,54,101,125,202,250,1111,1189,1207,1243,1255,
%T 1375,1405,1595,1779,1875,1877,1957,2008,2149,2175,2222,2235,2248,
%U 2272,2372,2378,2384,2414,2486,2500,2510,2552,2750,2757,2763,2781,2810,2840
%N Numbers k for which (phi(k))^2 + phi(k) + 1 is a palindrome.
%e 19 is in the sequence because (phi(19))^2 + phi(19) + 1 = 18^2 + 18 + 1 = 343, which is a palindrome.
%p rev:=proc(n) local nn: nn:=convert(n,base,10): add(nn[nops(nn)+1-j]*10^(j-1),j=1..nops(nn)) end: with(numtheory): a:=proc(m) if rev(phi(m)^2+phi(m)+1)=phi(m)^2+phi(m)+1 then m else fi end: seq(a(m),m=1..3500); # _Emeric Deutsch_, Apr 30 2006
%t Select[Range[3000],PalindromeQ[EulerPhi[#]^2+EulerPhi[#]+1]&] (* _Harvey P. Dale_, Jan 16 2024 *)
%K base,nonn
%O 1,2
%A Luc Stevens (lms022(AT)yahoo.com), Apr 24 2006
%E More terms from _Emeric Deutsch_, Apr 30 2006
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