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A134234 Triangle read by rows, n-th row = n terms of 2n, 2n+2, 2n+4, ..., 1; with a(1) = 1.

%I A134234 #11 Feb 08 2022 20:19:03
%S A134234 1,4,1,6,8,1,8,10,12,1,10,12,14,16,1,12,14,16,18,20,1,14,16,18,20,22,
%T A134234 24,1,16,18,20,22,24,26,28,1,18,20,22,24,26,28,30,32,1,20,22,24,26,28,
%U A134234 30,32,34,36,1
%N A134234 Triangle read by rows, n-th row = n terms of 2n, 2n+2, 2n+4, ..., 1; with a(1) = 1.
%C A134234 Row sums = A056108: (1, 5, 15, 31, 53, ...).
%H A134234 Robert Israel, <a href="/A134234/b134234.txt">Table of n, a(n) for n = 1..10011</a>
%F A134234 G.f.: 2*x/(1-x)^2 - 2*(2-x)/(1-x)*Sum_{n>=1} n*x^(n*(n+1)/2) + (3-x)/(1-x)*Sum_{n>=1} x^(n*(n+1)/2). - _Robert Israel_, Jan 15 2016
%e A134234 First few rows of the triangle:
%e A134234    1;
%e A134234    4,  1;
%e A134234    6,  8,  1;
%e A134234    8, 10, 12,  1;
%e A134234   10, 12, 14, 16, 1;
%e A134234   ...
%p A134234 seq(op([seq(2*n+2*k,k=0..n-2),1]),n=1..10); # _Robert Israel_, Jan 15 2016
%t A134234 Flatten[Table[Join[{1},Range[n,2n-3,2]],{n,4,30,2}]] (* _Harvey P. Dale_, Nov 06 2013 *)
%Y A134234 Cf. A056108.
%K A134234 nonn,tabl
%O A134234 1,2
%A A134234 _Gary W. Adamson_, Oct 14 2007