This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A117720 #10 Sep 16 2024 14:25:34
%S A117720 0,1,999,2558,2585,2855,3366,3636,3663,4444,5258,5285,5528,5582,5825,
%T A117720 5852,6336,6363,6633,8255,8525,8552,12489,12498,12849,12894,12948,
%U A117720 12984,13377,13737,13773,14289,14298,14829,14892,14928,14982,17337,17373
%N A117720 Numbers for which the sum of the digits is the square root of the product of their digits.
%H A117720 Harvey P. Dale, <a href="/A117720/b117720.txt">Table of n, a(n) for n = 0..1000</a>
%e A117720 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 A117720 sdsqrQ[n_]:=Module[{idn=IntegerDigits[n]},Total[idn]==Sqrt[Times@@idn]]; Select[Range[0,18000],sdsqrQ] (* _Harvey P. Dale_, Oct 20 2012 *)
%o A117720 (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) ; }
%o A117720 { 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 A117720 base,nonn
%O A117720 0,3
%A A117720 Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006
%E A117720 More terms from _R. J. Mathar_, Apr 21 2006