This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A215073 #6 Jul 22 2025 23:21:02 %S A215073 1,1,2,4,12,40,154,659,3085,15438,81200,442206,2465945,13968206, %T A215073 79933735,460447075,2663586832,15450089345,89773528848,522212524474 %N A215073 Number of squarefree words of length n in a 7-ary alphabet, with new values 0..6 introduced in increasing order. %C A215073 Column 6 of A215075 %e A215073 Some solutions for n=9 %e A215073 ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 %e A215073 ..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1 %e A215073 ..0....2....2....2....0....2....0....2....0....2....2....0....2....2....2....2 %e A215073 ..2....3....3....0....2....3....2....3....2....3....0....2....3....1....0....0 %e A215073 ..3....2....0....3....3....2....3....2....0....4....3....3....1....3....2....3 %e A215073 ..4....0....4....4....0....4....2....1....3....0....4....4....2....1....1....2 %e A215073 ..5....4....5....5....2....2....1....0....1....3....3....3....0....4....2....0 %e A215073 ..2....5....2....1....0....3....0....2....2....4....0....5....4....0....3....1 %e A215073 ..5....1....4....5....3....2....3....1....1....3....2....6....3....3....4....4 %K A215073 nonn %O A215073 1,3 %A A215073 _R. H. Hardin_ Aug 02 2012