A291869 Numbers n such that sigma(phi(n)) - phi(n) = n + phi(sigma(n)-n); that is, f(g(n)) - g(f(n)) = n where f = A001065 and g = A000010.

52298, 88694, 13868696, 18816288938

Offset

1,1

Comments

a(5) > 45*10^9. - Giovanni Resta, Sep 05 2017

Links

Table of n, a(n) for n=1..4.

Example

52298 is a term because phi(sigma(52298) - 52298) = phi(27382) = 13690, sigma(phi(52298)) - phi(52298) = sigma(25740) - 25740 = 65988 and 65988 - 13690 = 52298.

Prog

(PARI) a001615(n) = sigma(n)-n;
isok(n) = a001615(eulerphi(n))==n+eulerphi(a001615(n));

Crossrefs

Cf. A000010, A001065, A062401, A062402.

Sequence in context: A031679 A234679 A191303 * A186849 A107654 A345611

Adjacent sequences: A291866 A291867 A291868 * A291870 A291871 A291872

Keyword

nonn,more

Author

Altug Alkan, Sep 04 2017

Extensions

a(4) from Giovanni Resta, Sep 05 2017

Status

approved