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 A011185 A B_2 sequence: a(n) = least value such that sequence increases and pairwise sums of distinct elements are all distinct. 17
 1, 2, 3, 5, 8, 13, 21, 30, 39, 53, 74, 95, 128, 152, 182, 212, 258, 316, 374, 413, 476, 531, 546, 608, 717, 798, 862, 965, 1060, 1161, 1307, 1386, 1435, 1556, 1722, 1834, 1934, 2058, 2261, 2497, 2699, 2874, 3061, 3197, 3332, 3629, 3712, 3868, 4140, 4447, 4640 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = least positive integer > a(n-1) and not equal to a(i)+a(j)-a(k) for distinct i and j with 1 <= i,j,k <= n-1. [Comment corrected by Jean-Paul Delahaye, Oct 02 2020.] LINKS Klaus Brockhaus and Dan Hoey, Table of n, a(n) for n = 1..2839 Index entries for B_2 sequences. FORMULA a(n) = A010672(n-1)+1. PROG (Python) from itertools import islice def agen(): # generator of terms aset, sset, k = set(), set(), 0 while True: k += 1 while any(k+an in sset for an in aset): k += 1 yield k; sset.update(k+an for an in aset); aset.add(k) print(list(islice(agen(), 51))) # Michael S. Branicky, Feb 05 2023 CROSSREFS Cf. A010672. Cf. A033627, A003278, A026471, A066720, A075122, A075123, A133097. Cf. A036241, A349777. Sequence in context: A080787 A065124 A048817 * A240733 A283936 A278800 Adjacent sequences: A011182 A011183 A011184 * A011186 A011187 A011188 KEYWORD nonn AUTHOR Dan Hoey STATUS approved

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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)