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%I #13 Apr 26 2012 19:10:20
%S 1,1,20,3246670537110000
%N a(n) = (n!)!/(n!^(n-1)!).
%C n^(n-1)! divides (n!)! because the product (n!)! = 1*2*3*...*n*(n+1)*...*n! contains (n-1)! divisors such that n, 2n, 3n,...,(n-1)!*n = n!
%C a(5) contains 149 digits; a(6) contains 1404 decimal digits; a(7) contains 13808 decimal digits; a(8) contains 144975 decimal digits.
%p for n from 1 to 5 do: x:= (n!)!/(n!^(n-1)!): printf(`%d, `,k):od:
%Y Cf. A000142.
%K nonn
%O 1,3
%A _Michel Lagneau_, Apr 26 2012