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 A090377 #10 Jan 02 2021 14:57:23 %S A090377 1,2,4,10,26,66,173,456,1230,3318,9066,24768,68304,188370,523083, %T A090377 1452560,4054708,11318926 %N A090377 Number of configurations that require a minimum of n moves to be reached, starting with the empty square in one of the corners of an infinitely large extension of Sam Loyd's sliding block 15-puzzle. %C A090377 The first n terms of this sequence coincide with the first n terms of the corresponding sequences for n X n sliding block puzzles (see Cross-references). %o A090377 (Python) # uses alst(), swap() in A089473 %o A090377 nn = 13 %o A090377 start = "".join([chr(i) for i in range(45, 45+(nn+1)**2)]) # chr(45) is "-" %o A090377 print(alst(start, (nn+1, nn+1), maxd=nn)) # _Michael S. Branicky_, Jan 02 2021 %Y A090377 Cf. A089473 (3 X 3 puzzle), A089484 (4 X 4), A090031 (5 X 5), A090032 (6 X 6). %K A090377 more,nonn %O A090377 0,2 %A A090377 _Hugo Pfoertner_, Nov 27 2003 %E A090377 a(10)-a(17) from _Michael S. Branicky_, Dec 28 2020