%I A084602
%S A084602 1,1,1,3,1,2,7,6,9,1,3,12,19,36,27,27,1,4,18,40,91,120,162,108,81,1,5,
%T A084602 25,70,185,331,555,630,675,405,243,1,6,33,110,330,726,1441,2178,2970,
%U A084602 2970,2673,1458,729,1,7,42,161,539,1386,3157,5797,9471,12474,14553
%N A084602 Triangle, read by rows, where the n-th row lists the (2n+1) coefficients 
               of (1+x+3x^2)^n.
%e A084602 Rows:
%e A084602 {1},
%e A084602 {1,1,3},
%e A084602 {1,2,7,6,9},
%e A084602 {1,3,12,19,36,27,27},
%e A084602 {1,4,18,40,91,120,162,108,81},
%e A084602 {1,5,25,70,185,331,555,630,675,405,243},
%e A084602 {1,6,33,110,330,726,1441,2178,2970,2970,2673,1458,729},
%o A084602 (PARI) for(n=0,15, for(k=0,2*n,t=polcoeff((1+x+3*x^2)^n,k,x); print1(t",
               ")); print(" "))
%Y A084602 Cf. A002426, A084600-A084601, A084603-A084615.
%Y A084602 Sequence in context: A074305 A151855 A135338 this_sequence A100888 A052914 
               A131671
%Y A084602 Adjacent sequences: A084599 A084600 A084601 this_sequence A084603 A084604 
               A084605
%K A084602 nonn,tabl
%O A084602 0,4
%A A084602 Paul D. Hanna (pauldhanna(AT)juno.com), Jun 01 2003