%I #37 Jul 24 2021 01:12:01
%S 0,12,42,90,156
%N Numbers k such that k = (sum of digits of k)*((sum of digits of k) + 1).
%e 0 = 0*(0+1).
%e 12 = (1+2)*(1+2+1).
%e 42 = (4+2)*(4+2+1).
%e 90 = (9+0)*(9+0+1).
%e 156 = (1+5+6)*(1+5+6+1).
%t fQ[n_] := Block[{a = Plus @@ IntegerDigits@ n}, a*(a +1) == n]; Select[ Range[0, 1000], fQ] (* _Robert G. Wilson v_, Feb 24 2017 *)
%o (VBA)
%o Sub calcul()
%o Sheets("Result").Select
%o Range("A1").Select
%o For i = 1 To 10000000
%o Sum = 0
%o For k = 1 To Len(i)
%o Sum = Sum + Mid(i, k, 1)
%o Next
%o res = Sum * (Sum + 1)
%o If res = i Then
%o ActiveCell.Value = i
%o ActiveCell.Offset(1, 0).Select
%o End If
%o Next
%o End Sub
%K bref,base,fini,full,nonn
%O 1,2
%A _Shmelev Aleksei_, Feb 24 2017