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%I #22 Jun 13 2022 10:04:05
%S 24,30,126,150,198,276,280,294,336,1644,3084,3750,5720,13482,47424,
%T 211884,11718750,51028120,75570560,88590144,260661280,7435072458,
%U 7440172542,19408312640,184390255062,410770687360
%N Numbers k such that if x = sigma(k) - k then k = x - phi(x), where phi(k) is the Euler totient function.
%C Fixed points of the transform k -> sigma(k) - k - phi(sigma(k)-k).
%e sigma(276) = 672 and 672 - 276 = 396; phi(396) = 120 and 396 - 120 = 276.
%p with(numtheory); P:=proc(q) local n; k:=0;
%p for n from 1 to q do if 2*n=sigma(n)-phi(sigma(n)-n) then print(n);
%p fi; od; end: P(10^9);
%o (PARI) isok(n) = (x = sigma(n) - n) && (n == x - eulerphi(x)); \\ _Michel Marcus_, Mar 28 2014
%Y Cf. A000010, A000203, A239802.
%K nonn,more
%O 1,1
%A _Paolo P. Lava_, Mar 27 2014
%E a(17)-a(20) from _Michel Marcus_, Mar 28 2014
%E a(21)-a(24) from _Kevin P. Thompson_, Jan 14 2022
%E a(25) from _Kevin P. Thompson_, Apr 19 2022
%E a(26) from _Kevin P. Thompson_, Jun 13 2022
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