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 A130496 Repetition of even numbers, with initial zeros, five times. 1

%I

%S 0,0,0,0,0,2,2,2,2,2,4,4,4,4,4,6,6,6,6,6,8,8,8,8,8,10,10,10,10,10,12,

%T 12,12,12,12,14,14,14,14,14,16,16,16,16,16,18,18,18,18,18,20,20,20,20,

%U 20,22,22,22,22,22,24,24,24,24,24,26,26,26,26,26,28,28,28,28,28,30,30,30

%N Repetition of even numbers, with initial zeros, five times.

%F a(n)= -2 + 2*Sum_{k=0..n} {[8*(sin(2*Pi*k/5))^2-5]^2-5}/20, with n>=0. a(n)= -2 + 2*Sum_{k=0..n} 1/50*{-9*[k mod 5]+[(k+1) mod 5]+[(k+2) mod 5]+[(k+3) mod 5]+11*[(k+4) mod 5]}, with n>=0.

%F a(n)=-2+2*Sum{k=0..n}{1-(k^4 mod 5)}, with n>=0 [From _Paolo P. Lava_, Feb 17 2010]

%p P:=proc(n) local i,j,k; for i from 0 by 1 to n do j:=-2+2*sum('(8*(sin(2*Pi*k/5))^2-5)^2-5','k'=0..i)/20; print(j); od; end: P(100);

%t Table[#,5]&/@(2*Range[0,15])//Flatten (* _Harvey P. Dale_, Sep 11 2016 *)

%Y Cf. A122461.

%K easy,nonn

%O 0,6

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 31 2007

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Last modified June 21 11:57 EDT 2021. Contains 345363 sequences. (Running on oeis4.)