A393425 Numbers k such that sigma(k) = psi(k) + phi(k) + Omega(k)^4.

16688, 33592, 49808, 132928, 213568, 322660, 495808, 1826846464, 3139477866

Offset

1,1

Links

Table of n, a(n) for n=1..9.

Example

16688 is a term since sigma(16688) = 37200 = 28800 + 7104 + 6^4 = psi(16688) + phi(16688) + Omega(16688)^4.

Prog

(PARI) isok(k) = {my(f = factor(k)); sigma(f) == prod(i=1, #f~, (f[i, 1]+1) * f[i, 1]^(f[i, 2]-1)) + eulerphi(f) + bigomega(f)^4; } \\ Amiram Eldar, Feb 14 2026

Crossrefs

Cf. A000203, A001615, A000010, A001222, A390049, A393229, A393230.

Sequence in context: A108843 A232449 A260312 * A345573 A345829 A224572

Adjacent sequences: A393422 A393423 A393424 * A393426 A393427 A393428

Keyword

nonn,hard,more

Author

S. I. Dimitrov, Feb 14 2026

Extensions

a(8)-a(9) from Amiram Eldar, Feb 14 2026

Status

approved