Wieferich pairs and Barker sequences, II
Peter Borwein and Michael J. Mossinghoff

Three known values of u < 5 * 10^49 for which u has exactly four prime
factors, counting multiplicity, and n = 4u^2 cannot be eliminated as a
possible length of a Barker sequence.  Each value is shown with its prime
factorization.

1890448348089674770182781 [53, 97, 4794006457, 76704103313]
3080894677428239302747085 [5, 5333, 612142549, 188748146801]
19804304830012264298738041 [30109, 1128713, 2167849, 268813277]