Number of solutions to triples version of Langford (or Langford-Skolem) problem.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =3a(9) =5a(10) =0a(11) =0a(12) =0a(13) =0a(14) =0a(15) =0a(16) =13440a(17) =54947a(18) =249280a(19) =0a(20) =0a(21) =0a(22) =0a(23) =0a(24) =0