Number of n-length words over a quaternary alphabet {a_1,a_2,...,a_4} avoiding consecutive letters a_i, a_{i+1}.
A277667
Number of n-length words over a quaternary alphabet {a_1,a_2,...,a_4} avoiding consecutive letters a_i, a_{i+1}.
Terms
- a(0) =1a(1) =4a(2) =13a(3) =42a(4) =136a(5) =440a(6) =1423a(7) =4602a(8) =14883a(9) =48132a(10) =155660a(11) =503408a(12) =1628033a(13) =5265096a(14) =17027441a(15) =55067134a(16) =178088372a(17) =575941872a(18) =1862609199a(19) =6023720790a(20) =19480850935a(21) =63001517896a(22) =203748351160a(23) =658926832032
External references
- oeis: A277667