%I A118231
%S A118231 1,2,1,2,0,1,4,2,2,1,2,0,0,0,1,2,1,1,2,2,1,4,0,2,0,2,0,1,6,1,6,2,1,0,2,
               1,
%T A118231 4,0,1,0,3,0,2,0,1,6,1,6,4,1,2,4,2,2,1,4,0,3,0,1,0,2,0,0,0,1,4,0,3,1,1,
               1,
%U A118231 2,1,1,2,2,1,14,0,7,0,7,0,6,0,2,0,2,0,1,14,0,3,1,10,0,4,2,3,0,1,0,2,1
%V A118231 1,-2,1,-2,0,1,4,-2,-2,1,-2,0,0,0,1,2,1,1,-2,-2,1,4,0,-2,0,-2,0,1,-6,1,
               6,-2,1,0,-2,1,
%W A118231 -4,0,1,0,3,0,-2,0,1,6,-1,-6,4,-1,-2,4,-2,-2,1,-4,0,3,0,1,0,-2,0,0,0,1,
               4,0,-3,-1,-1,1,
%X A118231 2,1,1,-2,-2,1,14,0,-7,0,-7,0,6,0,-2,0,-2,0,1,-14,0,3,1,10,0,-4,-2,3,0,
               1,0,-2,1
%N A118231 Triangle, read by rows, equal to the matrix square of triangle A118229.
%C A118231 Describes the sequence transformation of triangle A118229 iterated twice. 
               Also equals the matrix inverse of triangle A118233.
%H A118231 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A118231 Triangle begins:
%e A118231 1;
%e A118231 -2, 1;
%e A118231 -2, 0, 1;
%e A118231 4,-2,-2, 1;
%e A118231 -2, 0, 0, 0, 1;
%e A118231 2, 1, 1,-2,-2, 1;
%e A118231 4, 0,-2, 0,-2, 0, 1;
%e A118231 -6, 1, 6,-2, 1, 0,-2, 1;
%e A118231 -4, 0, 1, 0, 3, 0,-2, 0, 1;
%e A118231 6,-1,-6, 4,-1,-2, 4,-2,-2, 1;
%e A118231 -4, 0, 3, 0, 1, 0,-2, 0, 0, 0, 1;
%e A118231 4, 0,-3,-1,-1, 1, 2, 1, 1,-2,-2, 1;
%e A118231 14, 0,-7, 0,-7, 0, 6, 0,-2, 0,-2, 0, 1; ...
%o A118231 (PARI) T(n,k)=if(n<k|k<0,0,(matrix(n,n,r,c,if(r>=c,if(gcd(r-c+1,c)==1,
               1,0)))^-2)[n,k])
%Y A118231 Cf. A118229, A118233 (inverse).
%Y A118231 Sequence in context: A156837 A129559 A129680 this_sequence A166453 A118233 
               A159955
%Y A118231 Adjacent sequences: A118228 A118229 A118230 this_sequence A118232 A118233 
               A118234
%K A118231 sign,tabl
%O A118231 1,2
%A A118231 Leroy Quet, Paul D. Hanna (pauldhanna(AT)juno.com), Apr 16 2006