Function: noun
Date: 1795
: a number (as 3, 6, 10, 15) representable by that many dots arranged in rows that form a triangle and that equals ( n ( n +1)/2) where n = 1, 2, 3, ⋯ for some positive integer value of n
Function: noun
Date: 1795
: a number (as 3, 6, 10, 15) representable by that many dots arranged in rows that form a triangle and that equals ( n ( n +1)/2) where n = 1, 2, 3, ⋯ for some positive integer value of n
Merriam Webster Collegiate English Dictionary. Merriam Webster - Энциклопедический словарь английского языка. 2012