A394609 - OEIS

A394609

Numbers k such that sigma(k) = psi(k) + phi(k) + pi(k).

108, 1949792, 5674984, 696281988, 1394173160, 1394174840, 1394179880, 1394181160, 1394182280, 1394182360

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

108 is a term since sigma(108) = 280 = 216 + 36 + 28 = psi(108) + phi(108) + pi(108).

PROG

(PARI) dedpsi(f) = prod(k = 1, #f~, (f[k, 1]+1) * f[k, 1]^(f[k, 2]-1));

list(lim) = {my(q = 2, m = 0, f); forprime(p = 3, lim, m++; for(k = q, p-1, f = factor(k); if(sigma(f) == dedpsi(f) + eulerphi(f) + m, print1(k, ", "))); q = p); } \\ Amiram Eldar, Mar 26 2026

CROSSREFS

Cf. A000010, A000203, A000720, A001615.

Sequence in context: A269269 A230474 A030248 * A033535 A077728 A093724

Adjacent sequences: A394606 A394607 A394608 * A394610 A394612 A394613

KEYWORD

nonn,hard,more

AUTHOR

S. I. Dimitrov, Mar 26 2026

EXTENSIONS

a(4)-a(10) from Amiram Eldar, Mar 26 2026

STATUS

approved