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%I #11 Mar 14 2014 07:11:11
%S 3,4,6,80,920,37568,56352,7148453888,7169453056,7286124544,7325797376,
%T 7595232256,8935567360,9107655680,13403351040
%N Let y be the sum of the numbers x coprime to n, with x<=n. Sequence lists n such that digits of y end in 'n'.
%C n*phi(n)/2 is of the form 'm' U 'n'.
%e phi(920) = 352; 902*352/2 = 161920 that is '161' U '920'.
%p with(numtheory); P:=proc(q) local a,b,n;
%p for n from 1 to q do a:=n; b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od;
%p if n=((n*phi(n)/2) mod 10^b) then print(n); fi; od; end: P(10^9);
%Y Cf. A000010, A239245.
%K nonn,more,base
%O 1,1
%A _Paolo P. Lava_, Mar 13 2014
%E a(8)-a(15) from _Giovanni Resta_, Mar 14 2014
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