Proof step

Ore-algebra identity of two definitions

All-n equality of two definitions

Concludes

shift_x_plus_one of Triangle read by rows: T(n,k) is the number of ternary words (i.e., finite sequences of 0's, 1's and 2's) of length n having k occurrences …

Premises

none: a direct theorem check

Theorem

polytool ?

Checked

polytool replayed · Lean not attempted