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

0, 12, 42, 90, 156

Offset

1,2

Links

Table of n, a(n) for n=1..5.

Example

    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).

Mathematica

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

Prog

(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

Crossrefs

Sequence in context: A085798 A335150 A270700 * A045945 A210206 A005901

Adjacent sequences: A282690 A282691 A282692 * A282694 A282695 A282696

Keyword

bref,base,fini,full,nonn

Author

Shmelev Aleksei, Feb 24 2017

Status

approved