%I A131081
%S A131081 8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,
%T A131081 1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,
%U A131081 4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8,7,4,1,0,1,4,7,8
%N A131081 Periodic sequence (8, 7, 4, 1, 0, 1, 4, 7).
%C A131081 Fourth column of triangular array T defined in A131074.
%F A131081 a(1) = 8, a(2) = a(8) = 7, a(3) = a(7) = 4, a(4) = a(6) = 1, a(5) = 0; 
               for n > 8, a(n) = a(n-8).
%F A131081 G.f.: (8-x-3*x^2-3*x^3+7*x^4)/((1-x)*(1+x^4)).
%F A131081 a(n)=1/56*{(n mod 8)-13*[(n+1) mod 8]-13*[(n+2) mod 8]+[(n+3) mod 8]+15*[(n+4) 
               mod 8]+29*[(n+5) mod 8]+29*[(n+6) mod 8]+15*[(n+7) mod 8]}, with 
               n>=0. - Paolo P. Lava (ppl(AT)spl.at), Jun 19 2007
%o A131081 (PARI) {m=105; for(n=1, m, r=(n-1)%8; print1(if(r==0, 8, if(r==1||r==7, 
               7, if(r==2||r==6, 4, if(r==4, 0, 1)))), ","))}
%o A131081 (MAGMA) m:=105; [ [8, 7, 4, 1, 0, 1, 4, 7][(n-1) mod 8 + 1]: n in [1..m] 
               ];
%Y A131081 Cf. A131074, A131028.
%Y A131081 Sequence in context: A073232 A086253 A094883 this_sequence A158288 A072102 
               A154815
%Y A131081 Adjacent sequences: A131078 A131079 A131080 this_sequence A131082 A131083 
               A131084
%K A131081 nonn
%O A131081 1,1
%A A131081 Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), following a suggestion 
               of Paul Curtz (bpcrtz(AT)free.fr), Jun 14 2007