Pentagonal Number

A polygonal number of the form n*(3n - 1)/2

0, 1, 5, 12, 22, 35, 51, 70, 92, 117, 145, 176, 210, 247, 287, 330, 376, 425, 477, 532, 590, 651, 715, 782, 852, 925, 1001, 1080, 1162, 1247, 1335, 1426, 1520, 1617, 1717, 1820, 1926, 2035, 2147, 2262, 2380, 2501, 2625, 2752, 2882, 3015, 3151

http://oeis.org/A000326

There are conjectured to be exactly 210 positive integers that cannot be represented using three pentagonal numbers, namely

There are six positive integers that cannot be expressed using four pentagonal numbers

http://mathworld.wolfram.com/PentagonalNumber.html

Questions:

(*) Find how pentagonal numbers relate to triangular numbers

(*) Show that every positive integer can be expressed as a sum of 5 or fewer pentagonal numbers