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Zimin Words and Bifixes
One of the earliest contributions to the OnLine Encyclopedia of Integer Sequences (OEIS) was a family sequences counting the number of words that begin (or don’t begin) with a palindrome: Let \(f_k(n)\) be the number of strings of length \(n\)…

My Favorite Sequences: A263135
This is the fourth in my installment of My Favorite Sequences. This post discusses sequence A263135 which counts pennytopenny connections among \(n\) pennies on the vertices of a hexagonal grid. I published this sequence in October 2015 when I was…

My Favorite Sequences: “Not Equal” Grid
This is the third installment in a recurring series, My Favorite Sequences. This post discusses OEIS sequence A278299, a sequence that took over two years to compute enough terms to add to the OEIS with confidence that it was distinct.…