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 A047875 #10 Apr 11 2025 08:47:48 %S A047875 7,1,5,9,8,9,9,4,8,7,9,9,9,9,8,9,6,9,8,8,9,8,8,7,9,8,7,8,8,9,8,8,9,9, %T A047875 8,9,9,9,9,8,9,6,8,9,10,9,9,8,6,7,8,8,8,9,8,9,9,9,10,9,9,8,9,9,7,9,9, %U A047875 9,9,8,9,9,7,8,8,9,9,7,8,7,9,9,9,9,9,9,8,9,9,9,9,9,9,9,8,9,9,8,9,9,9 %N A047875 Size of smallest polyomino with surround number n (the surround number of a polyomino is the number of different ways that it can be surrounded by non-overlapping copies of the same polyomino). %D A047875 W. F. Lunnon, Counting polyominoes, pp. 347-372 of A. O. L. Atkin and B. J. Birch, editors, Computers in Number Theory. Academic Press, NY, 1971. %H A047875 Giovanni Resta, <a href="/A047875/b047875.txt">Table of n, a(n) for n = 0..1000</a> (first 101 terms from Brendan Owen) %H A047875 E. J. Friedman, <a href="https://erich-friedman.github.io/mathmagic/0599.html">Math. Magic</a> %e A047875 a(2) = 5 because the smallest polyomino which has a surround number 2 is %e A047875 ..X.. %e A047875 .XXX. %e A047875 ..X.. %Y A047875 Cf. A000105. %K A047875 nonn %O A047875 0,1 %A A047875 Brendan Owen (bdowen(AT)ee.mu.oz.au) %E A047875 a(64) corrected by _Giovanni Resta_, Apr 09 2025