A393550 - OEIS

%I #23 Mar 24 2026 15:02:46

%S 1,320793350,485567925,905738150,1751006325,9169290725,9881908925

%N Numbers k such that sigma(k) = psi(k) + pi(k) + Omega(k)^9.

%e 320793350 is a term since sigma(320793350) = 597336768 = 578067840 + 17315803 + 5^9 = psi(320793350) + pi(320793350) + Omega(320793350)^9.

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

%o list(lim) = {my(q = 2, m = 0, f); print1(1, ", "); forprime(p = 3, lim, m++; for(k = q, p-1, f = factor(k); if(sigma(f) == dedpsi(f) + m + bigomega(f)^9, print1(k, ", "))); q = p); } \\ _Amiram Eldar_, Mar 20 2026

%Y Cf. A000203, A000720, A001615, A001222, A393162, A393163, A393123, A394260, A394312, A394315, A394402, A394403.

%K nonn,hard,more

%O 1,2

%A _S. I. Dimitrov_, Mar 20 2026

%E a(5)-a(7) from _Amiram Eldar_, Mar 20 2026