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Squares that are the sum of exactly three distinct powers of 2.
4

%I #15 Nov 23 2018 10:30:14

%S 25,49,81,100,196,289,324,400,529,784,1089,1156,1296,1600,2116,3136,

%T 4225,4356,4624,5184,6400,8464,12544,16641,16900,17424,18496,20736,

%U 25600,33856,50176,66049,66564,67600,69696,73984,82944,102400,135424,200704,263169

%N Squares that are the sum of exactly three distinct powers of 2.

%C Squares with exactly three ones in their binary representation: A000120(a(n)) = 3;

%C squares in A014311;

%C a(n) = A212191(n)^2.

%H Giovanni Resta, <a href="/A212190/b212190.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Reinhard Zumkeller)

%t Select[Range[1000]^2, DigitCount[#, 2, 1] == 3&] (* _Jean-François Alcover_, Nov 07 2016 *)

%o (Haskell)

%o a212190 n = a212190_list !! (n-1)

%o a212190_list = filter ((== 1) . a010052) a014311_list

%Y Cf. A010052, A212192.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, May 03 2012