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%I #21 Sep 10 2019 22:21:31
%S 0,1,1,2,2,5,2,4,5,3,7,5,10,2,8,4,5,6,11,32,42,68,24,87
%N Number of values of m such that sigma(m) = A002110(n) where A002110(n) is the product of the first n primes.
%H Max A. Alekseyev, <a href="https://www.emis.de/journals/JIS/VOL19/Alekseyev/alek5.html">Computing the Inverses, their Power Sums, and Extrema for Euler's Totient and Other Multiplicative Functions</a>. Journal of Integer Sequences, Vol. 19 (2016), Article 16.5.2.
%F a(n) = A054973(A002110(n)). - _Ray Chandler_, Dec 28 2008
%e a(10) = 3 because 2388809736, 3450503048 and 3696967556 are the only numbers with a sigma value = A002110(10). A002110(10) = 6469693230 = 2*3*5*7*11*13*17*19*23*29.
%Y Cf. A000203, A002110, A153076, A153077.
%K nonn,more
%O 1,4
%A _Donovan Johnson_, Dec 19 2008
%E a(12)-a(21) from _Ray Chandler_, Dec 28 2008
%E a(22)-a(24) from _Max Alekseyev_, Jan 27 2012