Number of 3n-length n-ary words, either empty or beginning with the first letter of the alphabet, that can be built by repeatedly inserting triples of identical letters into the initially empty word.
A218472
Number of 3n-length n-ary words, either empty or beginning with the first letter of the alphabet, that can be built by repeatedly inserting triples of identical letters into the initially empty word.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =61a(4) =1810a(5) =82593a(6) =5153626a(7) =410380885a(8) =39868799482
External references
- oeis: A218472