From George Gilbert's marks problem: jumping 4 marks at a time (final positions).

Terms

a(0) =2a(1) =4a(2) =47a(3) =233a(4) =477a(5) =538a(6) =1163a(7) =4544a(8) =23938a(9) =47952a(10) =74329a(11) =385194a(12) =424332a(13) =838758a(14) =3601963a(15) =8880674a(16) =9376182a(17) =10177957a(18) =10622608a(19) =12051969a(20) =14306604a(21) =23190118a(22) =25373883a(23) =28661729a(24) =138953419a(25) =1150488807a(26) =1204511338