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A282693 Numbers k such that k = (sum of digits of k)*((sum of digits of k) + 1). 0
0, 12, 42, 90, 156 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 26 20:49 EST 2022. Contains 350599 sequences. (Running on oeis4.)