login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A256020 a(n) = Sum_{i=1..n-1} (i^4 * a(i)), a(1)=1. 2

%I

%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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 25 01:17 EDT 2019. Contains 321450 sequences. (Running on oeis4.)