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Product_{k=1..n} k^(k^4).
15

%I #16 Sep 08 2015 13:44:16

%S 1,65536,29060398333495723291328487792256607374737408

%N Product_{k=1..n} k^(k^4).

%C The next term a(4) has 198 digits.

%H Vaclav Kotesovec, <a href="/A255323/b255323.txt">Table of n, a(n) for n = 1..5</a>

%F a(n) ~ A243264 * n^(n*(n+1)*(2*n+1)*(3*n^2+3*n-1)/30) / exp(n^5/25 - n^3/12 + 13*n/360), where A243264 = exp(-3*Zeta(5)/(4*Pi^4)).

%t Table[Product[k^(k^4), {k, 1, n}], {n, 1, 5}]

%o (PARI) a(n)=prod(k=1,n,k^k^4) \\ _Charles R Greathouse IV_, Sep 08 2015

%Y Cf. A002109, A051675, A255321, A255344, A013663, A243264.

%K nonn

%O 1,2

%A _Vaclav Kotesovec_, Feb 21 2015