A300487 Numbers k whose 10's complement mod 10 of their digits is equal to phi(k), the Euler totient function of k.
74, 834, 80940, 809400, 833334, 7414114, 7422694, 7539694, 8094000, 80940000, 809400000, 8094000000, 80940000000, 83335786566, 809400000000, 7539682539694, 8094000000000, 80940000000000
Offset: 1
Examples
phi(74) = 36 that is the 10's complement of the digits of 74.
Programs
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Maple
with(numtheory): P:=proc(q) local a,b,k,n; for n from 1 to q do a:=convert(phi(n),base,10); for k from 1 to nops(a) do a[k]:=(10-a[k]) mod 10; od; b:=0; for k from 1 to nops(a) do b:=b*10+a[nops(a)-k+1]; od; if b=n then print(n); fi; od; end: P(10^9);
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PARI
isok(x) = {my(dx = digits(x), dy = vector(#dx, k, (10-dx[k]) % 10)); fromdigits(dy) == eulerphi(x); } \\ Michel Marcus, Mar 12 2018
Extensions
a(11)-a(15) from Giovanni Resta, Mar 09 2018
a(16)-a(18) from Max Alekseyev, Mar 09 2024
Comments