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 A117720 Numbers for which the sum of the digits is the square root of the product of their digits. 4

%I #6 Oct 20 2012 17:47:41

%S 0,1,999,2558,2585,2855,3366,3636,3663,4444,5258,5285,5528,5582,5825,

%T 5852,6336,6363,6633,8255,8525,8552,12489,12498,12849,12894,12948,

%U 12984,13377,13737,13773,14289,14298,14829,14892,14928,14982,17337,17373

%N Numbers for which the sum of the digits is the square root of the product of their digits.

%H Harvey P. Dale, <a href="/A117720/b117720.txt">Table of n, a(n) for n = 0..1000</a>

%e 2558 is in the sequence because (1)the sum of its digits is 2+5+5+8=20,(2)the product of its digits is 2*5*5*8=400 and 20 is the square root of 400.

%t sdsqrQ[n_]:=Module[{idn=IntegerDigits[n]},Total[idn]==Sqrt[Times@@idn]]; Select[Range[0,18000],sdsqrQ] (* _Harvey P. Dale_, Oct 20 2012 *)

%o (PARI) sudig(i,suOrmul)= { local(nshft,resul) ; nshft = i ; resul = nshft % 10 ; nshft = nshft \ 10 ; while(nshft>0, if(suOrmul==0, resul += nshft % 10, resul *= nshft % 10 ) ; nshft \= 10 ; ) ; return(resul) ; } { for(n=0,15000, summ = sudig(n,0) ; mull = sudig(n,1) ; if( summ^2==mull, print1(n,",") ) ; ) ; } - _R. J. Mathar_, Apr 21 2006

%K base,nonn

%O 0,3

%A Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006

%E More terms from _R. J. Mathar_, Apr 21 2006

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