Truncated triangular number
From Innerpedia - Encyclopedia of Torah's Inner Dimension - Chassidut and Kabbalah
The first positive truncated triangular number occurs for n=6. The truncated triangular numbers under 1000 are:
(See sequence A051938 in the Online encyclopedia of integer sequences)
Figurate form of the truncated triangular number
The figurate form of these numbers is a triangle of size n, with the 3 corner triangles of size 6 each truncated (cut off).
Truncated triangles and chemistry
37 is the truncated triangular form of 10 = 55, since 37 = 55 - 18. Another relationship between 37 and 55 appears in the opening words of Ecclesiastes "All is vaporous"<ref name="eccles1">Ecclesiastes 1:2</ref> (הַכֹּל הָבֶל), alluding to the "vaporous" nature of the elements, as follows.
The 3 numbers preceding 37 in the series are 10, 18, and 27, whose sum is 55. The value of the 4 consecutive numbers in the series 10, 18, 27, and 37 is 92, the number of naturally occuring elements (from hydrogen to uranium).