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 A139218 #7 Apr 26 2023 10:03:21
%S A139218 2,5,8,14,23,41,92,179,353,716,1427,2849,5708,11411
%N A139218 Smallest positive integer of the form 3k+2 such that all subsets of {a(1),...,a(n)} have a different sum.
%C A139218 (1) It appears that {a(n+1)-2a(n)} is eventually periodic, with values {1,-2,-2,-5,-5,10,-5,-5,10,-5,-5,10,-5,...}.
%C A139218 (2) See A139217 for the corresponding sequence using integers of the form 3k+1.
%C A139218 (3) _M. F. Hasler_, in a SeqFan memo dated Apr 09 2008, notes that the Jacobsthal sequence (A001045) from a(2) on (i.e., 1,3,5,11,21,...) gives the smallest positive odd integer such that all subsets of {a(2),...,a(n)} have a different sum.
%F A139218 It appears that a(n) = a(n-1)+a(n-2)+2*a(n-3), for n>6.
%Y A139218 Cf. A001045, A139217.
%K A139218 nonn
%O A139218 1,1
%A A139218 _John W. Layman_, Apr 11 2008