OFFSET
1,2
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
KEYWORD
bref,base,fini,full,nonn
AUTHOR
Shmelev Aleksei, Feb 24 2017
STATUS
approved