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A117720 Numbers for which the sum of the digits is the square root of the product of their digits. 4
0, 1, 999, 2558, 2585, 2855, 3366, 3636, 3663, 4444, 5258, 5285, 5528, 5582, 5825, 5852, 6336, 6363, 6633, 8255, 8525, 8552, 12489, 12498, 12849, 12894, 12948, 12984, 13377, 13737, 13773, 14289, 14298, 14829, 14892, 14928, 14982, 17337, 17373 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
EXAMPLE
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.
MATHEMATICA
sdsqrQ[n_]:=Module[{idn=IntegerDigits[n]}, Total[idn]==Sqrt[Times@@idn]]; Select[Range[0, 18000], sdsqrQ] (* Harvey P. Dale, Oct 20 2012 *)
PROG
(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
CROSSREFS
Sequence in context: A317594 A226752 A043527 * A110401 A213156 A164813
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006
EXTENSIONS
More terms from R. J. Mathar, Apr 21 2006
STATUS
approved

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Last modified April 16 10:37 EDT 2024. Contains 371709 sequences. (Running on oeis4.)