Number of irredundant sets in the n-ladder graph.

Terms

a(0) =3a(1) =11a(2) =26a(3) =79a(4) =224a(5) =640a(6) =1828a(7) =5225a(8) =14928a(9) =42654a(10) =121873a(11) =348232a(12) =995003a(13) =2843014a(14) =8123337a(15) =23210809a(16) =66320216a(17) =189496620a(18) =541448364a(19) =1547079580a(20) =4420468031a(21) =12630596045a(22) =36089381477a(23) =103118131368a(24) =294639269914a(25) =841872308017