The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A003044 For n > 4, a(n) is the least integer > a(n-1) with precisely two representations a(n) = a(i) + a(j), 1 <= i < j < n; and a(n) = n for n=1..4. (Formerly M0506) 3
 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 17, 19, 29, 31, 33, 43, 44, 47, 51, 54, 58, 68, 69, 78, 79, 86, 95, 99, 110, 113, 117, 133, 134, 135, 145, 151, 156, 159, 173, 180, 183, 193, 197, 204, 211, 229, 232, 236, 239, 243, 250, 256, 264, 270, 281, 284 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First differs from A060470 at a(13) = 29. - Peter Munn, Dec 10 2017 REFERENCES S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 145-151. R. K. Guy, Unsolved Problems in Number Theory, Section C4. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n = 1..5440 Steven R. Finch, Ulam s-Additive Sequences [From Steven Finch, Apr 20 2019] R. Queneau, Sur les suites s-additives, J. Combin. Theory, A12 (1972), 31-71. Queneau left out 44. MATHEMATICA a[n_ /; n <= 4] = n; a[n_] := a[n] = Catch[ For[an = a[n-1] + 1, True, an++, cnt = 0; Do[If[an == a[i] + a[j], cnt++], {i, 1, n-1}, {j, i+1, n-1}]; If[cnt == 2, Throw[an]]]]; Table[a[n], {n, 1, 56}](* Jean-François Alcover, Apr 30 2012 *) PROG (Haskell) a003044 n = a003044_list !! (n-1) a003044_list = 1 : 2 : 3 : 4 : f [4, 3..1] where    f xs@(x:_) = y : f (y : xs) where      y = head [w | w <- [x + 1 ..],          length [() | v <- xs, (w - v) `elem` dropWhile (>= v) xs] == 2] -- Reinhard Zumkeller, Mar 17 2013 CROSSREFS Cf. A060470. Sequence in context: A018350 A033058 A060470 * A279077 A018541 A018293 Adjacent sequences:  A003041 A003042 A003043 * A003045 A003046 A003047 KEYWORD nonn,nice AUTHOR EXTENSIONS Name edited by Michel Marcus, Dec 11 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 26 01:25 EDT 2020. Contains 337346 sequences. (Running on oeis4.)