A230372 Numbers n such that phi(sigma(n)) = sigma(n) - phi(n).

2, 3, 5, 119, 143, 287, 623, 3983, 6851, 7429, 13727, 18601, 37213, 48209, 118921, 181559, 322889, 423181, 891157, 926041, 961727, 1115261, 1150747, 1656857, 1693081, 1799063, 2219693, 2303653, 2325983, 2350337, 2539273, 2752463, 2755841, 3320291, 3624887

Offset

1,1

Links

Donovan Johnson, Table of n, a(n) for n = 1..535 (terms < 3*10^10)

Example

phi(119) = 96, sigma(119) = 144, phi(144) = 48 and 144 - 96 = 48.

Maple

with(numtheory); P:=proc(q) local n;
for n from 1 to q do
if phi(sigma(n))=sigma(n)-phi(n) then print(n);
fi; od; end: P(10^6);

Crossrefs

Cf. A000010, A000203, A062401, A230023, A230371.

Sequence in context: A118505 A067799 A321362 * A234900 A117702 A041343

Adjacent sequences: A230369 A230370 A230371 * A230373 A230374 A230375

Keyword

nonn

Author

Paolo P. Lava, Oct 17 2013

Extensions

a(22) - a(35) from Donovan Johnson, Oct 21 2013

Status

approved