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 A227221 #21 Sep 26 2024 17:10:38 %S A227221 1,9,33,79,154,266,423,632,900,1235,1644,2135,2714,3390,4170,5061, %T A227221 6071,7206,8475,9885,11443,13157,15034,17082,19307,21718,24322,27126, %U A227221 30137,33363,36812,40491,44407,48568,52980,57652,62592,67805,73300,79084,85165,91550,98246 %N A227221 Volume of Johnson square pyramid placed upright on cube (rounded down) with edge lengths equal to n. %C A227221 Johnson square pyramid: a square base with four equilateral triangle- faces. It is placed upright on top of the cube. All the edge lengths are equal. %H A227221 Georg Fischer, <a href="/A227221/b227221.txt">Table of n, a(n) for n = 1..1000</a> [first 203 terms from _K. D. Bajpai_] %H A227221 Wikipedia, <a href="http://en.wikipedia.org/wiki/Square_pyramid">Square pyramid</a> %e A227221 a(4) = 79: volume = sqrt(2)/6*k^3 + k^3 = sqrt(2)/6*4^3 + 4^3 = 79.0849... and floor(79.0849...) = 79. %p A227221 a:= n-> floor((sqrt(2)/6 + 1)*n^3): %p A227221 seq(a(n), n=1..43); %Y A227221 Cf. A224837. %K A227221 nonn %O A227221 1,2 %A A227221 _K. D. Bajpai_, Sep 19 2013