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 A220661 #18 Mar 31 2025 22:31:46 %S A220661 1,1,2,1,2,3,4,5,6,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20, %T A220661 21,22,23,24,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22, %U A220661 23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39 %N A220661 Irregular table, where the n-th row consists of numbers 1..n! %H A220661 Antti Karttunen, <a href="/A220661/b220661.txt">The rows 1..7 of the irregular table, flattened.</a> %F A220661 a(n) = n - A007489(A084556(n)-1). %F A220661 a(n) = A220660(n)+1. %e A220661 Rows of this irregular table begin as: %e A220661 1; %e A220661 1, 2; %e A220661 1, 2, 3, 4, 5, 6; %t A220661 Flatten[Range[#]&/@(Range[5]!)] (* _Harvey P. Dale_, Apr 20 2013 *) %o A220661 (Scheme) (define (A220661 n) (- n (A007489 (-1+ (A084556 n))))) %Y A220661 Cf. A000142, A220660. %K A220661 nonn,tabf %O A220661 1,3 %A A220661 _Antti Karttunen_, Dec 18 2012