Diagonal sums of number a triangle related to the Pell numbers.

Terms

a(0) =1a(1) =-2a(2) =-1a(3) =-4a(4) =-5a(5) =-6a(6) =-11a(7) =-8a(8) =-19a(9) =-10a(10) =-29a(11) =-12a(12) =-41a(13) =-14a(14) =-55a(15) =-16a(16) =-71a(17) =-18a(18) =-89a(19) =-20a(20) =-109a(21) =-22a(22) =-131a(23) =-24a(24) =-155a(25) =-26a(26) =-181a(27) =-28a(28) =-209a(29) =-30