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 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). 1
 0, 3, 10, 21, 153, 210, 378, 496, 820, 1431, 3081, 4656, 8646, 11628, 15051, 17766, 22578, 26335, 32896, 37950, 46665, 53301, 64620, 73153, 87571, 98346, 108345, 113526, 130305, 162735, 185136, 193131, 218791, 267546, 300700, 312445, 349866 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sides of the successive triangles are given by A158031. Terms computed by Jean-Marc Falcoz. REFERENCES Mohammad K. Azarian, A Trigonometric Characterization of  Equilateral Triangle, Problem 336, Mathematics and Computer Education, Vol. 31, No. 1, Winter 1997, p. 96.  Solution published in Vol. 32, No. 1, Winter 1998, pp. 84-85. Mohammad K. Azarian, Equating Distances and Altitude in an Equilateral Triangle, Problem 316, Mathematics and Computer Education, Vol. 28, No. 3, Fall 1994, p. 337.  Solution published in Vol. 29, No. 3, Fall 1995, pp. 324-325. LINKS Eric Angelini, Digit Spiral E. Angelini, Digit Spiral [Cached copy, with permission] EXAMPLE ...0....0....0.....0 ........13...13....13 .............610...610 ...................1521 The triangular numbers fitting exactly in the SE corner of the above triangles are 0, 3, 10, 21. CROSSREFS Sequence in context: A120109 A286067 A337623 * A068082 A058077 A161672 Adjacent sequences:  A158027 A158028 A158029 * A158031 A158032 A158033 KEYWORD base,nonn AUTHOR Eric Angelini, Mar 11 2009 STATUS approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)