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A249065 Numbers n such that n = concatenate(a, b) and sigma(a) + sigma(b) = phi(n).

%I A249065 #5 Nov 01 2014 02:19:20
%S A249065 12,420,966,2700,5700,5940,7440,12540,71100,76680,107880,118680,
%T A249065 121920,156420,160650,161880,259080,284580,339150,353430,395850,
%U A249065 498420,585200,600780,701220,746130,752100,771420,870870,1052220,1249680,1654620,1684020,1696080
%N A249065 Numbers n such that n = concatenate(a, b) and sigma(a) + sigma(b) = phi(n).
%e A249065 For n = 966 we can consider 966 as 96 U 6; sigma(96) + sigma(6) = 252 + 12 = 264 = phi(966).
%p A249065 with(numtheory); P:=proc(q) local a,b,i,n; for n from 1 to q do
%p A249065 for i from 1 to ilog10(n) do a:=trunc(n/10^i); b:=n-a*10^i;
%p A249065 if sigma(a)+sigma(b)=phi(n) then print(n); break;
%p A249065 fi; od; od; end: P(10^9);
%Y A249065 Cf. A000005, A000203, A239562.
%K A249065 nonn,base
%O A249065 1,1
%A A249065 _Paolo P. Lava_, Oct 20 2014