Search: id:A036744
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%I A036744
%S A036744 139854276,152843769,157326849,215384976,245893761,254817369,326597184,
%T A036744 361874529,375468129,382945761,385297641,412739856,523814769,529874361,
%U A036744 537219684,549386721,587432169,589324176,597362481,615387249,627953481,
               653927184,672935481,697435281,714653289,735982641,743816529,842973156,
               847159236,923187456
%N A036744 Penholodigital squares: squares containing each of the digits 1..9 exactly 
               once.
%C A036744 Improved Mathematica formula provided. Because the range involved is 
               only from Ceiling[Sqrt[123456789]]=11112 and Floor[Sqrt[987654321]]=31427, 
               it only requires analyzing 20,315 numbers, versus 362,880 permutations 
               of nine digits (as in the current formula). - Harvey P. Dale (hpd1(AT)nyu.edu), 
               Apr 17 2002
%C A036744 Since the sum of the digits is 45, the squares are all divisible by 3, 
               so the given Mathematica formula could be sped up by a factor of 
               3, checking only multiples of 3 rather than all squares. - Joshua 
               Zucker (joshua.zucker(AT)stanfordalumni.org), Nov 28 2005
%t A036744 Select[Range[11112, 31427]^2, Union[Drop[DigitCount[ # ], -1]] == {1} 
               &]
%Y A036744 Sequence in context: A105297 A034642 A109093 this_sequence A075130 A034611 
               A160688
%Y A036744 Adjacent sequences: A036741 A036742 A036743 this_sequence A036745 A036746 
               A036747
%K A036744 fini,nonn,full
%O A036744 1,1
%A A036744 David W. Wilson (davidwwilson(AT)comcast.net)
%E A036744 More terms from Harvey P. Dale (hpd1(AT)nyu.edu), Sep 26 2001

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