A053919 - OEIS

%I #23 Feb 29 2024 23:08:44

%S 25,225,55225,235225,3553225,33235225,252333225,2523555225,3325252225,

%T 5232352225,3235555525225,232555332555225,35232553232323225,

%U 32355552523523552532225,25532532332552235533223325522255225,332222523225232223533222222253253255253352335533253225

%N Squares composed of digits {2,3,5}.

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>

%H Author?, <a href="http://web.archive.org/web/20080708203024/http://blue.kakiko.com/mmrmmr/htm/eqtn06.html">Source</a>(<a href="http://web.archive.org/web/20060426155831/http://blue.kakiko.com/mmrmmr/txt/eqtn06.txt">txt</a>)

%H H. Mishima <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#235">Squares consisted of 3 different digits</a>

%F a(n) = A053918(n)^2.

%o (Python) # see link in A053918 for a faster version

%o from math import isqrt

%o def aupto(limit):

%o   alst, rootlimit = [], isqrt(limit)

%o   for k in range(1, rootlimit+1):

%o     if set(str(k*k)) <= set("235"): alst.append(k*k)

%o   return alst

%o print(aupto(4*10**12)) # _Michael S. Branicky_, May 15 2021

%Y Cf. A053918.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Mar 15 2000

%E More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 03 2005

%E One more term from Mishima's webpage added by _Max Alekseyev_, Jun 17 2011

%E a(16) from _Zhao Hui Du_, Feb 29 2024