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 A080500 #3 Dec 05 2013 19:56:00 %S A080500 1,1,2,3,4,10,18,28,40,54,140,264,432,650,924,1260,1664,4284,8100, %T A080500 13376,20400,29484,40964,55200,72576,93500,236808,443232,728000, %U A080500 1108380,1603800,2235968,3028992,4009500,5206760,6652800,8382528,20867704 %N A080500 a(n) = (n-1)(n-4)(n-9)...(n-k^2) where k^2 < n <= (k+1)^2. %C A080500 The idea of A080497 to A080500 when applied to Euler's phi function i.e. on phi-torial function defined in A001783 yields A001783 itself for obvious reasons. Is there any other such example? %e A080500 a(6) = (6-1)(6-4)= 10. %Y A080500 Cf. A080497, A080498, A072513. %K A080500 nonn %O A080500 1,3 %A A080500 _Amarnath Murthy_, Mar 19 2003 %E A080500 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003