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A030193 Let S = squares; a(0)=0; a(n) = smallest m such that m - a(i) is not in S for any i < n. 3
0, 2, 5, 7, 10, 12, 15, 17, 20, 22, 34, 39, 44, 52, 57, 62, 65, 67, 72, 85, 95, 109, 119, 124, 127, 130, 132, 137, 142, 147, 150, 170, 177, 180, 182, 187, 192, 197, 204, 210, 215, 238, 243, 249, 255, 257, 260, 262, 267 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Consider the following game: two players make moves in turn, initially the number on the board is n, each move consists of subtracting a perfect square from the number on the board, the player who faces 0 loses. This sequence is the set of losing positions in this game. - Mikhail Dvorkin (mikhail.dvorkin(AT)gmail.com), Jan 27 2008

This sequence was investigated by Golomb (1966), who proved that it is infinite. More strongly (as Ruzsa 1984 notes) the number of values up to any given n is at least proportional to sqrt(n). No two numbers in this sequence differ by a square, and this sequence can be defined as the lexicographically first (greedy) sequence with no square differences. It follows from the Furstenberg-Sárközy theorem (e.g., see Sárközy 1978) that its natural density is zero. - David Eppstein, Nov 20 2016

LINKS

Karl W. Heuer, Table of n, a(n) for n = 0..61299

S. W. Golomb, A mathematical investigation of games of "take-away", J. Combinatorial Theory, 1 (1966), 443-458.

I. Ruzsa, Difference sets without squares, Period. Math. Hungar. 15 (1984), no. 3, 205-209.

A. Sárközy, On difference sets of sequences of integers I, Acta Mathematica Academiae Scientiarum Hungarica, March 1978, Volume 31, Issue 1, pp 125-149.

A. Sárközy, On difference sets of sequences of integers III, Acta Mathematica Academiae Scientiarum Hungarica, September 1978, Volume 31, Issue 3, pp 355-386.

A. Sárközy, On the difference sets of sequences of integers II, Eotvos Sect. Math. 21(1978), 45-53.

MATHEMATICA

moves[n_] := Table[n - i^2, {i, 1, Sqrt[n]}]; gana[n_] := Which[n == 0, False, True, !Select[moves[n], !gana[#] &] =={}]; Select[Range[155] - 1, ! gana[#] &] (* José María Grau Ribas, Jul 19 2013 *)

CROSSREFS

Sequence in context: A038126 A047215 A059536 * A028250 A190087 A182771

Adjacent sequences:  A030190 A030191 A030192 * A030194 A030195 A030196

KEYWORD

nonn,changed

AUTHOR

Jan Kristian Haugland (jankrihau(AT)hotmail.com)

EXTENSIONS

More terms from Karl W. Heuer, Jun 13 2013

STATUS

approved

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Last modified December 4 17:40 EST 2016. Contains 278755 sequences.