Number of Bottleneck-Monge matrices with 4 rows.

Terms

a(0) =16a(1) =87a(2) =384a(3) =1516a(4) =5535a(5) =19030a(6) =62347a(7) =196301a(8) =597725a(9) =1768733a(10) =5105853a(11) =14423037a(12) =39968765a(13) =108884733a(14) =292116989a(15) =772923389a(16) =2019573757a(17) =5216813053a(18) =13334904829a(19) =33758183421a(20) =84702265341a(21) =210777210877a(22) =520498839549