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%I #10 Nov 27 2013 15:32:35
%S 3,5,18,38,94,114,130,168,198,202,222,238,247,314,495,518,531,612,630,
%T 662,722,754,812,914,969,1007,1125,1138,1254,1258,1260,1313,1316,1558,
%U 1665,1736,1778,1794,1957,2110,2138,2233,2279,2327,2360,2364,2385,2474
%N Sigma(n)+phi(n) is a triangular number.
%H Charles R Greathouse IV, <a href="/A069066/b069066.txt">Table of n, a(n) for n = 1..10000</a>
%t triangularQ[n_] := IntegerQ[ Sqrt[8n + 1] ]; Select[ Range[2500], triangularQ[ DivisorSigma[1, #] + EulerPhi[#]] &] (* _Jean-François Alcover_, Jul 17 2013 *)
%o (PARI) is(n)=ispolygonal(sigma(n=factor(n))+eulerphi(n),3) \\ _Charles R Greathouse IV_, Nov 27 2013
%K nonn
%O 1,1
%A _Benoit Cloitre_, Apr 05 2002