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%I #20 Feb 28 2022 12:08:42
%S 2,3,4,5,6,7,8,9,10,11,12,14,15,16,17,18,19,20,21,22,23,24,25,26,27,
%T 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,
%U 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71
%N Numbers that can be written as sum of a positive squarefree number and a positive square.
%C Subsequence of A011760; A085263(a(n)) > 0.
%C Conjecture: a(n) = n + 2 for n > 11. That is, only 1 and 13 are missing. - _Charles R Greathouse IV_, Aug 21 2011
%C Estermann proves that only finitely many positive integers are missing from this sequence. (Probably only 1 and 13.) - _Charles R Greathouse IV_, Jul 01 2016
%H Theodor Estermann, <a href="https://eudml.org/doc/159528">Einige Sätze über quadratfreie Zahlen</a>, Mathematische Annalen 105:1 (1931), pp. 653-662.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquareNumber.html">Square Number</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Squarefree.html">Squarefree</a>
%o (PARI) is(n)=forstep(k=sqrtint(n-1), 1, -1, if(issquarefree(n-k^2), return(1))); 0 \\ _Charles R Greathouse IV_, Mar 12 2012
%K nonn,easy
%O 1,1
%A _Reinhard Zumkeller_, Jun 23 2003
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