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 A118489 #9 Jul 06 2021 15:49:26 %S A118489 0,1,16,25,49,100,400,576,900,1024,1089,1521,1600,2025,2209,2304,2401, %T A118489 2500,2601,2704,2809,3025,3600,4096,4900,5041,5625,6084,6400,7056, %U A118489 8100,9025,9409,9604,9801,10000,10201,10404,10609,10816,11025,11236,12100,14400 %N A118489 Squares for which the product of the digits is a triangular number. %C A118489 Includes all squares not in A052041. - _Robert Israel_, May 25 2020 %H A118489 Robert Israel, <a href="/A118489/b118489.txt">Table of n, a(n) for n = 1..10000</a> %e A118489 26569 is in the sequence because (1) it is a square, (2) the product of its digits is 2*6*5*6*9=3240 which is a triangular number. %p A118489 filter:= n -> issqr(1+8*convert(convert(n,base,10),`*`)): %p A118489 select(filter, [seq(i^2,i=1..1000)]); # _Robert Israel_, May 25 2020 %t A118489 Select[Range[0,120]^2,OddQ[Sqrt[8 (Times@@IntegerDigits[#]) +1]]&] (* _Harvey P. Dale_, Jul 06 2021 *) %Y A118489 Cf. A000217, A052041. %K A118489 base,nonn %O A118489 1,3 %A A118489 Luc Stevens (lms022(AT)yahoo.com), May 05 2006 %E A118489 1600 inserted by _Robert Israel_, May 25 2020