a pronic number, oblong number, rectangular number or heteromecic number, is a number which is the product of two consecutive integers, that is, n&nbsp;(n&nbsp;+&nbsp;1). the n-th pronic number is twice the n-th triangular number and n more than the n-th square number. the first few pronic numbers  are: :0, 2, 6, 12, 20, 30, 42, 56, 72, 90, 110, 132, 156, 182, 210, 240, 272, 306, 342, 380, 420, 462 â¦ these numbers are sometimes called oblong because they are analogous to polygonal numbers in this way: :{| style="text-align: center" |- valign="bottom" |style="padding: 0 1em"|16px|* 16px|* |style="padding: 0 1em"|16px|* 16px|* 16px|*16px|* 16px|* 16px|* |style="padding: 0 1em"|16px|* 16px|* 16px|* 16px|*16px|* 16px|* 16px|* 16px|*16px|* 16px|* 16px|* 16px|* |style="padding: 0 1em"|16px|* 16px|* 16px|* 16px|* 16px|*16px|* 16px|* 16px|* 16px|* 16px|*16px|* 16px|* 16px|* 16px|* 16px|*16px|* 16px|* 16px|* 16px|* 16px|* |- |1Ã2||2Ã3||3Ã4||4Ã5 |} pronic numbers can also be expressed as nÂ²&nbsp;+&nbsp;n. the n-th pronic number is the sum of the first n even integers, as well as the difference between (2n&nbsp;&minus;&nbsp;1)Â² and the n-th centered hexagonal number. all pronic numbers are even, therefore 2 is the only prime pronic number. it is also the only pronic number in the fibonacci sequence and the only pronic lucas number.wayne l. mcdaniel, "pronic lucas numbers", the fibonacci quarterly, vol.36, iss.1, pp.60-62, 1998.wayne l. mcdaniel, "pronic fibonacci numbers", the fibon
Figurate_numbers Integer_sequences