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 A277904 #11 Nov 16 2016 11:08:03 %S A277904 0,0,0,1,0,1,0,1,2,3,0,1,2,3,0,1,2,3,4,5,0,1,2,3,4,5,0,1,2,3,4,5,6,7, %T A277904 8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,10,11,12,13,0,1,2,3,4,5, %U A277904 6,7,8,9,10,11,12,13,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 %N A277904 Irregular table: row n (n >= 0) is obtained by listing numbers 0 .. A018819(n)-1. %H A277904 Antti Karttunen, <a href="/A277904/b277904.txt">Table of n, a(n) for n = 1..9828</a> %F A277904 a(1) = 0; for n > 1, a(n) = n - A000123(A277903(n)-1) - 1. %e A277904 A018819 -> range -> terms on row n %e A277904 1 [0,0]: 0; %e A277904 1 [0,0]: 0; %e A277904 2 [0,1]: 0, 1; %e A277904 2 [0,1]: 0, 1; %e A277904 4 [0,3]: 0, 1, 2, 3; %e A277904 4 [0,3]: 0, 1, 2, 3; %e A277904 6 [0,5]: 0, 1, 2, 3, 4, 5; %e A277904 etc. %o A277904 (Scheme) (define (A277904 n) (if (= 1 n) 0 (- n (A000123 (+ -1 (A277903 n))) 1))) %Y A277904 Cf. A000123, A018819, A277903. %Y A277904 Used for constructing A277905. %Y A277904 Retaining only every second row gives A278164. %K A277904 nonn,tabf %O A277904 1,9 %A A277904 _Antti Karttunen_, Nov 14 2016