a(n) = number of n-lettered words in the alphabet {1, 2, 3, 4} with as many occurrences of the substring (consecutive subword) [1, 2] as of [2, 1].
A211307
a(n) = number of n-lettered words in the alphabet {1, 2, 3, 4} with as many occurrences of the substring (consecutive subword) [1, 2] as of [2, 1].
Terms
- a(0) =1a(1) =4a(2) =14a(3) =52a(4) =192a(5) =716a(6) =2680a(7) =10080a(8) =38064a(9) =144288a(10) =548864a(11) =2094640a(12) =8017760a(13) =30774656a(14) =118422080a(15) =456752512a(16) =1765443584a(17) =6837128064a(18) =26525842176a(19) =103080123392a(20) =401172719104
External references
- oeis: A211307