A282693 Numbers k such that k = (sum of digits of k)*((sum of digits of k) + 1).

0, 12, 42, 90, 156

Offset: 1

Author

Shmelev Aleksei, Feb 24 2017

Keywords

• bref
• base
• fini
• full
• nonn

Examples

			    0 = 0*(0+1).
   12 = (1+2)*(1+2+1).
   42 = (4+2)*(4+2+1).
   90 = (9+0)*(9+0+1).
  156 = (1+5+6)*(1+5+6+1).
		

Programs

Mathematica

fQ[n_] := Block[{a = Plus @@ IntegerDigits@ n}, a*(a +1) == n]; Select[ Range[0, 1000], fQ] (* Robert G. Wilson v, Feb 24 2017 *)

VBA

Sub calcul()
   Sheets("Result").Select
   Range("A1").Select
   For i = 1 To 10000000
      Sum = 0
      For k = 1 To Len(i)
         Sum = Sum + Mid(i, k, 1)
      Next
      res = Sum * (Sum + 1)
      If res = i Then
         ActiveCell.Value = i
         ActiveCell.Offset(1, 0).Select
      End If
   Next
End Sub