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 A021733 #37 Jun 12 2025 09:30:26
%S A021733 0,0,1,3,7,1,7,4,2,1,1,2,4,8,2,8,5,3,2,2,3,5,9,3,9,6,4,3,3,4,7,0,5,0,
%T A021733 7,5,4,4,5,8,1,6,1,8,6,5,5,6,9,2,7,2,9,7,6,6,8,0,3,8,4,0,8,7,7,9,1,4,
%U A021733 9,5,1,9,8,9,0,2,6,0,6,3,1,0,0,1,3,7,1,7,4,2,1,1,2,4,8,2,8,5,3
%N A021733 Decimal expansion of 1/729.
%C A021733 729 = 3^6 = 9^3 = 27^2.
%C A021733 Period is 81 = 9^2 (see example for all 81 digits of the repeating part).
%C A021733 Repeating part in the form of 9 X 9 square table:
%C A021733 1, 3, 7, 1, 7, 4, 2, 1, 1,
%C A021733 2, 4, 8, 2, 8, 5, 3, 2, 2,
%C A021733 3, 5, 9, 3, 9, 6, 4, 3, 3,
%C A021733 4, 7, 0, 5, 0, 7, 5, 4, 4,
%C A021733 5, 8, 1, 6, 1, 8, 6, 5, 5,
%C A021733 6, 9, 2, 7, 2, 9, 7, 6, 6,
%C A021733 8, 0, 3, 8, 4, 0, 8, 7, 7,
%C A021733 9, 1, 4, 9, 5, 1, 9, 8, 9,
%C A021733 0, 2, 6, 0, 6, 3, 1, 0, 0.
%C A021733 Note that each column consists of 9 consecutive (cyclically repeated) digits out of 10. The missing digits in columns from left to right are {7, 6, 5, 4, 3, 2, 0, 9, 8}, which form also a cycle of 9 out of 10 consecutive digits in reverse order, all digits except 1. - _Alexander Adamchuk_, Dec 28 2013
%F A021733 Equals Sum_{k>=1} (k*(k+1)/2)/10^(k+2). - _Davide Rotondo_, Jun 11 2025
%e A021733 1/729 = 0.00137174211248285322359396433470507544581618655692729766\
%e A021733 803840877914951989026063100 (period 81). - _Alexander Adamchuk_, Dec 28 2013
%t A021733 RealDigits[1/729, 10, 100] (* _Alexander Adamchuk_, Dec 28 2013 *)
%o A021733 (PARI) 1/729. \\ _Michel Marcus_, Oct 28 2019
%Y A021733 Cf. A068542 (period of the fraction 1/3^n).
%Y A021733 Cf. A010701 (1/3), A000012 (1/9), A021031 (1/27), A021085 (1/81).
%K A021733 nonn,cons
%O A021733 0,4
%A A021733 _N. J. A. Sloane_