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 A145017 #23 Jul 16 2025 13:49:47
%S A145017 1,2,5,10,13,17,26,29,34,37,53,58,65,73,82,85,97,101,109,122,130,137,
%T A145017 145,170,173,178,185,194,197,205,221,226,229,241,257,265,281,290,293,
%U A145017 298,305,314,349,362,365,370,377,386,397,401,409,442,445,457,466,485,493
%N A145017 Squarefree positive integers k for which k-(floor(sqrt(k)))^2 is a perfect square.
%C A145017 If an odd prime p divides a(n) then it has the form 4k+1.
%C A145017 Conjecture. For every n>=1 there exist infinitely many primes p of the form 4k+1 for which for a(n) > 1 we have s*p-(floor(sqrt(s*p)))^2 is not a perfect square for s=1,...,a(n)-1 while a(n)*p-(floor(sqrt(a(n)*p)))^2 is a perfect square. (See A145016(s=1) and A145022, A145023, A145047, A145048, A145049, A145050 correspondingly for s=2, s=5, s=10, s=13, s=17, s=26.) - _Vladimir Shevelev_, Sep 30 2008
%H A145017 Andrew Howroyd, <a href="/A145017/b145017.txt">Table of n, a(n) for n = 1..1000</a>
%t A145017 Select[Range@ 500, And[SquareFreeQ@ #, IntegerQ@ Sqrt[# - Floor[Sqrt@ #]^2]] &] (* _Michael De Vlieger_, Jan 12 2020 *)
%o A145017 (PARI) is(n)={issquarefree(n) && issquare(n-sqrtint(n)^2)} \\ _Andrew Howroyd_, Jan 12 2020
%Y A145017 Cf. A005117, A020893, A145016, A145022, A145023, A145047, A145048, A145049, A145050.
%K A145017 nonn
%O A145017 1,2
%A A145017 _Vladimir Shevelev_, Sep 29 2008
%E A145017 Missing a(40) inserted and terms a(42) and beyond from _Andrew Howroyd_, Jan 12 2020