A131508 - OEIS

%I #9 Oct 24 2018 22:53:32

%S 0,0,0,2,1,1,1,4,2,2,2,6,3,3,3,8,4,4,4,10,5,5,5,12,6,6,6,14,7,7,7,16,

%T 8,8,8,18,9,9,9,20,10,10,10,22,11,11,11,24,12,12,12,26,13,13,13,28,14,

%U 14,14,30,15,15,15,32,16,16,16,34,17,17,17,36,18,18,18,38,19,19,19,40,20

%N 2*A000027 (natural numbers) sandwiched by tripled A001477 (nonnegative numbers).

%H Muniru A Asiru, <a href="/A131508/b131508.txt">Table of n, a(n) for n = 0..5000</a>

%F From _Chai Wah Wu_, Oct 24 2018: (Start)

%F a(n) = 2*a(n-4) - a(n-8) for n > 7.

%F G.f.: x^3*(x^3 + x^2 + x + 2)/(x^8 - 2*x^4 + 1). (End)

%p seq(coeff(series(x^3*(x^3+x^2+x+2)/(x^8-2*x^4+1),x,n+1), x, n), n = 0 .. 85); # _Muniru A Asiru_, Oct 24 2018

%o (GAP)  a:=[0,0,0,2,1,1,1,4];; for n in [9..85] do a[n]:=2*a[n-4]-a[n-8]; od; a; # _Muniru A Asiru_, Oct 24 2018

%K nonn,easy,less

%O 0,4

%A _Paul Curtz_, Aug 13 2007