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A256020
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a(n) = Sum_{i=1..n-1} (i^4 * a(i)), a(1)=1.
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2
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1, 1, 17, 1394, 358258, 224269508, 290877551876, 698687879606152, 2862524242746404744, 18783884080901907930128, 187857624693099981209210128, 2750611340756369924865254694176, 57039427373264843131930786593127712, 1629160124635190449534207126672913710144
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OFFSET
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1,3
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LINKS
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FORMULA
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Product_{i=2..n-1} (i^4 + 1), for n>2.
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.
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MATHEMATICA
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Clear[a]; a[1]=1; a[n_]:= a[n] = Sum[i^4*a[i], {i, 1, n-1}]; Table[a[n], {n, 1, 15}]
Flatten[{1, 1, Table[Product[(i^4 + 1), {i, 2, n-1}], {n, 3, 15}]}]
Join[{1}, FoldList[Times, Range[15]^4+1]/2] (* Harvey P. Dale, Jul 29 2018 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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