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 A117140 a(1)=5, a(2)=7; for n >= 3, a(n) is smallest number which is uniquely of the form a(j)+a(k) with 1<=j
 5, 7, 12, 17, 19, 22, 26, 27, 32, 33, 36, 37, 40, 42, 46, 50, 56, 60, 66, 70, 71, 74, 81, 85, 91, 99, 101, 132, 138, 140, 150, 154, 156, 158, 160, 179, 181, 185, 189, 195, 205, 209, 233, 234, 236, 240, 248, 258, 264, 268, 287, 289, 293, 297, 303, 336, 340, 342, 348 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS An Ulam-type sequence - see A002858 for many further references, comments, etc. Does not seem to have any nice periodicity like A007300 does. - Joshua Zucker, May 24 2006 LINKS T. D. Noe, Table of n, a(n) for n=1..10000 A. N. Debono, Ulam Sequences Eric Weisstein's World of Mathematics, Ulam Sequence Wikipedia, Ulam number MATHEMATICA max=100; A117140 = {5, 7}; Do[ AppendTo[ A117140, n = Last[A117140]; While[n++; Length[ DeleteCases[ Intersection[A117140, n - A117140], n/2, 1, 1]] != 2]; n], {max}]; A117140 (* Jean-François Alcover, Nov 30 2011 *) PROG (Haskell) a117140 n = a117140_list !! (n-1) a117140_list = 5 : 7 : ulam 2 7 a117140_list -- Function ulam as defined in A002858. -- Reinhard Zumkeller, Nov 03 2011 CROSSREFS Sequence in context: A314308 A314309 A314310 * A263536 A314311 A031144 Adjacent sequences:  A117137 A117138 A117139 * A117141 A117142 A117143 KEYWORD nonn AUTHOR N. J. A. Sloane, Apr 29 2006 EXTENSIONS More terms from Joshua Zucker, May 24 2006 STATUS approved

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Last modified January 28 23:08 EST 2022. Contains 350670 sequences. (Running on oeis4.)