A390579 Numbers k such that sigma(k) = psi(k) + phi(k) + tau(k)^4.

2488020, 8312128, 9451284, 14422164, 15247776, 16619824, 16705056, 29320404, 30312852, 30633728, 36265524, 38607060, 41223444, 58638372, 64988052, 68943444, 85736724, 94616052, 96904284, 100574672, 113335764, 114998848, 118256244, 119240052, 122068092, 124157652

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Example

2488020 is in the sequence since sigma(2488020) = 6966624 = 5971392 + 663456 + 24^4 = psi(2488020) + phi(2488020) + tau(2488020)^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) + numdiv(f)^4; } \\ Amiram Eldar, Nov 11 2025

Crossrefs

Cf. A000005, A000010, A000203, A001615, A388001, A389546, A390421, A390578.

Sequence in context: A180705 A286036 A215814 * A114659 A179733 A234910

Adjacent sequences: A390576 A390577 A390578 * A390580 A390581 A390582

Keyword

nonn

Author

S. I. Dimitrov, Nov 11 2025

Extensions

a(8) onward from Amiram Eldar, Nov 11 2025

Status

approved