This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 Harvey P. Dale, Table of n, a(n) for n = 0..1000 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 Adjacent sequences:  A117717 A117718 A117719 * A117721 A117722 A117723 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 19 03:15 EDT 2019. Contains 328211 sequences. (Running on oeis4.)