1. Tetrahedral numberA tetrahedral number, or triangular pyramidal number, is a figurate number that represents a pyramid with a triangular base and three sides, called a tetrahedron. The nth tetrahedral number is the sum of the first n triangular numbers. The first few tetrahedral numbers are: 1, 4, 10, 20, 35, 56, 84, 120, 165, 220, 286, 364, 455, 560, 680, 816, 969, …
Read “Tetrahedral number” on English Wikipedia
Read “三角錐数” on Japanese Wikipedia
Read “Tetrahedral number” on DBpedia
Read “Tetrahedral number” on English Wikipedia
Read “三角錐数” on Japanese Wikipedia
Read “Tetrahedral number” on DBpedia
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