A321581 a(n) is the sum of first n natural numbers raised to the product of first n natural numbers.
0, 1, 9, 46656, 1000000000000000000000000
Offset: 0
Examples
a(3) = (1+2+3)^3! = 6^6 = 46656.
Programs
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GAP
List([1..5], n->(n*(n+1)/2)^(Factorial(n))); # Stefano Spezia, Nov 21 2018
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Maple
[(n*(n+1)/2)^factorial(n)$n=0..5]; # Muniru A Asiru, Dec 20 2018
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Mathematica
a[n_] := (n*(n + 1)/2)^n!; Array[a, 5] (* Amiram Eldar, Nov 13 2018 *)
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PARI
a(n)=(n*(n+1)/2)^(n!); \\ Andrew Howroyd, Nov 13 2018
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