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 A138857 #18 Apr 07 2025 14:30:17
%S A138857 1,2,3,4,6,9,12,18,25,34,49,70,99,140,198,280,396,560,792,1120,1584,
%T A138857 2241,3169,4482,6339,8965,12678,17930,25357,35860,50714,71721,101429,
%U A138857 143442,202858,286885,405717,573770,811434,1147541,1622868,2295082,3245736,4590164,6491473,9180329,12982946,18360658,25965892,36721317,51931785,73442634,103863570,146885269,207727140,293770539
%N A138857 Numbers such that all subsets of {a(1)^2,...,a(n)^2} have a different sum.
%C A138857 Since the ratio of two successive terms of A138858 tends to 1:2, we have here lim a(n+1)/a(n) = sqrt(2). More precisely, one has a(n) ~ 2^(n/2+const.).
%C A138857 See A138858 for more comments.
%H A138857 Martin Fuller, <a href="/A138857/b138857.txt">Table of n, a(n) for n = 1..1000</a>
%F A138857 A138857(n)=sqrt(A138858(n))
%o A138857 (PARI) {s=1;p=0; for( n=1,23, until( !bitand( s, s>>(p^2) ), p++); s+=s<<(p^2); print1( p,","))}
%Y A138857 Cf. A138858(n)=a(n)^2, A138856, A138000, A138001, A064934, A382381.
%K A138857 nonn
%O A138857 1,2
%A A138857 _M. F. Hasler_, Apr 09 2008
%E A138857 a(24)-a(30) from _Donovan Johnson_, Oct 03 2009
%E A138857 a(31) onwards from _Martin Fuller_, Apr 07 2025