cp's OEIS Frontend

A158030 Triangular numbers t such that all the digits needed to write the consecutive triangular numbers from 0 to t fill exactly an equilateral triangle (no holes, no overlaps).

%I A158030 #9 Jul 07 2023 14:40:29
%S A158030 0,3,10,21,153,210,378,496,820,1431,3081,4656,8646,11628,15051,17766,
%T A158030 22578,26335,32896,37950,46665,53301,64620,73153,87571,98346,108345,
%U A158030 113526,130305,162735,185136,193131,218791,267546,300700,312445,349866
%N A158030 Triangular numbers t such that all the digits needed to write the consecutive triangular numbers from 0 to t fill exactly an equilateral triangle (no holes, no overlaps).
%C A158030 The sides of the successive triangles are given by A158031. Terms computed by Jean-Marc Falcoz.
%H A158030 Eric Angelini, <a href="http://www.cetteadressecomportecinquantesignes.com/DigitSpiral.htm">Digit Spiral</a>
%H A158030 E. Angelini, <a href="/A158022/a158022.pdf">Digit Spiral</a> [Cached copy, with permission]
%e A158030 ...0....0....0.....0
%e A158030 ........13...13....13
%e A158030 .............610...610
%e A158030 ...................1521
%e A158030 The triangular numbers fitting exactly in the SE corner of the above triangles are 0, 3, 10, 21.
%K A158030 base,nonn
%O A158030 1,2
%A A158030 _Eric Angelini_, Mar 11 2009