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%I #11 Dec 11 2023 08:37:06
%S 1,2,2,6,4,2,4,4,4,4,6,4,12,10,8,48,8,4,8,4,16,16,8,8,4,8,8,16,24,2,8,
%T 4,8,32,8,32,4,8,4,24,16,8,32,8,16,24,40,16,16,8,8,16,24,8,16,8,16,6,
%U 32,8,8,16,8,512,48,16,12,48,16,8,8,4,24,16,2,256
%N Number of divisors of n*2^n - 1, the Woodall (or Riesel) numbers.
%H Amiram Eldar, <a href="/A366898/b366898.txt">Table of n, a(n) for n = 1..865</a>
%F a(n) = sigma0(n*2^n - 1) = A000005(A003261(n)).
%t Table[DivisorSigma[0, n*2^n - 1], {n, 1, 100}] (* _Amiram Eldar_, Dec 11 2023 *)
%o (PARI) a(n) = numdiv(n*2^n - 1); \\ _Amiram Eldar_, Dec 11 2023
%Y Cf. A000005, A003261, A002234, A242273, A063515, A056821, A367006, A366899.
%K nonn
%O 1,2
%A _Tyler Busby_, Oct 26 2023
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