Square array read by ascending antidiagonals: number of m-shape Euler numbers.

Terms

a(0) =1a(1) =1a(2) =-1a(3) =1a(4) =-1a(5) =1a(6) =1a(7) =-1a(8) =1a(9) =-5a(10) =1a(11) =-1a(12) =5a(13) =-1a(14) =21a(15) =1a(16) =-1a(17) =19a(18) =-61a(19) =1a(20) =-105a(21) =1a(22) =-1a(23) =69a(24) =-1513a(25) =1385a(26) =-1a(27) =635a(28) =1a(29) =-1