A symmetrical triangle sequence:q=4:t(n,m,q)=(1 - q^n)*Eulerian[n + 1, m] - (1 - q^n) + 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =-44a(5) =1a(6) =1a(7) =-629a(8) =-629a(9) =1a(10) =1a(11) =-6374a(12) =-16574a(13) =-6374a(14) =1a(15) =1a(16) =-57287a(17) =-307922a(18) =-307922a(19) =-57287a(20) =1a(21) =1a(22) =-487304a(23) =-4873049a(24) =-9889424a(25) =-4873049a(26) =-487304a(27) =1a(28) =1a(29) =-4030217