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%I #22 Dec 11 2023 08:37:10
%S 0,1,1,3,2,1,2,2,2,2,3,2,4,5,4,6,3,2,3,2,4,5,3,3,2,3,3,4,5,1,3,2,3,5,
%T 3,5,2,3,2,5,4,3,5,3,4,5,7,4,4,3,3,4,5,3,4,3,4,3,5,3,3,4,3,9,6,4,4,6,
%U 4,3,3,2,5,4,1,9,3,4,5,2,1,4,5,6,2,3,4
%N Number of prime factors of n*2^n - 1, counted with multiplicity.
%C The numbers n*2^n-1 are called Woodall (or Riesel) numbers.
%H Amiram Eldar, <a href="/A366899/b366899.txt">Table of n, a(n) for n = 1..865</a>
%F a(n) = bigomega(n*2^n - 1) = A001222(A003261(n)).
%t Table[PrimeOmega[n*2^n - 1], {n, 1, 100}] (* _Amiram Eldar_, Dec 09 2023 *)
%o (PARI) a(n) = bigomega(n*2^n - 1); \\ _Michel Marcus_, Dec 09 2023
%Y Cf. A001222, A003261, A085723, A366898 (divisors), A367006 (without multiplicity).
%K nonn
%O 1,4
%A _Tyler Busby_, Oct 26 2023