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%I #9 Jul 29 2018 20:14:52
%S 1,1,17,1394,358258,224269508,290877551876,698687879606152,
%T 2862524242746404744,18783884080901907930128,
%U 187857624693099981209210128,2750611340756369924865254694176,57039427373264843131930786593127712,1629160124635190449534207126672913710144
%N a(n) = Sum_{i=1..n-1} (i^4 * a(i)), a(1)=1.
%F Product_{i=2..n-1} (i^4 + 1), for n>2.
%F a(n) ~ (cosh(Pi/sqrt(2))^2 * sin(Pi/sqrt(2))^2 + cos(Pi/sqrt(2))^2 * sinh(Pi/sqrt(2))^2) / (2*Pi^2) * ((n-1)!)^4.
%F a(n) = A255434(n-1)/2.
%t Clear[a]; a[1]=1; a[n_]:= a[n] = Sum[i^4*a[i],{i,1,n-1}]; Table[a[n],{n,1,15}]
%t Flatten[{1,1, Table[Product[(i^4 + 1), {i,2,n-1}],{n,3,15}]}]
%t Join[{1},FoldList[Times,Range[15]^4+1]/2] (* _Harvey P. Dale_, Jul 29 2018 *)
%Y Cf. A001710, A051893, A256019.
%K nonn
%O 1,3
%A _Vaclav Kotesovec_, Mar 13 2015
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