Number of meanders in which first bridge is 7.

Terms

a(0) =14a(1) =14a(2) =36a(3) =57a(4) =155a(5) =316a(6) =902a(7) =2053a(8) =6059a(9) =14810a(10) =44842a(11) =115009a(12) =355293a(13) =943860a(14) =2963536a(15) =8086913a(16) =25733325a(17) =71725012a(18) =230811370a(19) =654472364a(20) =2126296860a(21) =6115504594a(22) =20032488714a(23) =58309793101a(24) =192375702851a(25) =565712237384