a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 4, |s(i) - s(i-1)| <= 1 for i >=2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also a(n) = T(n,n-4), where T is the array in A026268.
A026290
a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 4, |s(i) - s(i-1)| <= 1 for i >=2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also a(n) = T(n,n-4), where T is the array in A026268.
Terms
- a(0) =1a(1) =4a(2) =14a(3) =46a(4) =145a(5) =446a(6) =1349a(7) =4034a(8) =11966a(9) =35290a(10) =103642a(11) =303458a(12) =886548a(13) =2585922a(14) =7534245a(15) =21934524a(16) =63826041a(17) =185668816a(18) =540034074a(19) =1570719570a(20) =4568920029a(21) =13292253106a(22) =38679350746a(23) =112583530784a(24) =327793747775a(25) =954702193796
External references
- oeis: A026290