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Numbers k such that usigma(k) = k + phi(k).
0

%I #20 Jul 17 2023 06:05:51

%S 2,28,1368,1700,342000,2061000,2120832,65834560,89082000

%N Numbers k such that usigma(k) = k + phi(k).

%C No other terms < 2700000000. - _Jud McCranie_, Nov 04 2001

%o (PARI) us(n) = sumdiv(n,d, if(gcd(d,n/d)==1,d));

%o for(n=1,10^8, if(us(n)==n+eulerphi(n),print1(n, ", ")))

%Y Cf. A000010, A034448, A121048.

%K nonn,more

%O 1,1

%A _Jason Earls_, Aug 18 2001

%E More terms from _Jud McCranie_, Nov 04 2001

%E Offset corrected by _Mohammed Yaseen_, Jul 17 2023