A393090 - OEIS

%I #12 Feb 05 2026 16:20:10

%S 1,16,30915,1439284375,3200409125

%N Numbers k such that sigma(k) = psi(k) + pi(k) + omega(k)^7.

%e 30915 is a term since sigma(30915) = 55200 = 49680 + 3333 + 3^7 = psi(30915) + pi(30915) + omega(30915)^7.

%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 + omega(f)^7, print1(k, ", "))); q = p); } \\ _Amiram Eldar_, Feb 01 2026

%Y Cf. A000203, A000720, A001615, A001221, A390234, A390235, A390236, A392053, A392054, A392909.

%K nonn,hard,more

%O 1,2

%A _S. I. Dimitrov_, Feb 01 2026

%E a(4)-a(5) from _Amiram Eldar_, Feb 02 2026