Question 480578
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
{2,4,36,__,150,180,...}

Note:  {{{a[1]}}} = 1^2*2 (n+1)
 {{{a[2]}}} = 2^2 * (n-1)
 {{{a[3]}}} = 3^2*(n+1)
etc
{{{a[n] = n^2(n + (-1)^(n+1))}}}

  {{{a[4]}}} = 16*(4-1) = 15*3 = 48