Numerators in triangle that leads to the (first) Bernoulli numbers A027641/A027642.

Terms

a(0) =1a(1) =1a(2) =-3a(3) =1a(4) =-5a(5) =5a(6) =1a(7) =-7a(8) =25a(9) =-5a(10) =1a(11) =-9a(12) =23a(13) =-35a(14) =49a(15) =1a(16) =-11a(17) =73a(18) =-27a(19) =112a(20) =-49a(21) =1a(22) =-13a(23) =53a(24) =-77a(25) =629a(26) =-91a(27) =58a(28) =1a(29) =-15