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A273041 Discriminator of the Catalan numbers A000108. 2
1, 2, 5, 5, 11, 11, 16, 16, 23, 23, 23, 23, 47, 47, 64, 64, 64, 64, 71, 71, 141, 141, 141, 141, 173, 173, 173, 173, 173, 173, 173, 201, 251, 251, 251, 251, 251, 251, 251, 313, 313, 313, 383, 383, 383, 383, 383, 519, 519, 519, 519, 519, 519, 519, 519, 519, 601, 601, 601, 601, 601, 601, 601, 601, 601, 601 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The discriminator of a sequence is the least positive integer k such that the first n terms of the sequence are pairwise distinct modulo k.

LINKS

Robert Israel, Table of n, a(n) for n = 1..1127

MAPLE

N = 100: # to get a(1) .. a(N)

F:= proc(m)

  local G, i, j, x, S;

  G:= 1+x; S:= {1};

  for i from 2 do

    G:= convert(series((x*G^2-1)/(2*x*G-1), x, 2^i+1), polynom) mod m;

    for j from 2^(i-1) to 2^i do

      S:= S union {coeff(G, x, j)};

      if nops(S) < j then return j-1 fi

    od:

  od

end proc:

nmax:= 1: A[1]:= 1:

for k from 2 while nmax < N do

  v:= F(k);

  if v > nmax then

    for j from nmax+1 to v do A[j]:= k od:

    nmax:= v;

  fi:

od:

seq(A[i], i=1..N); # Robert Israel, May 13 2016

CROSSREFS

Cf. A000108.

Sequence in context: A081467 A194119 A084721 * A274108 A138316 A183719

Adjacent sequences:  A273038 A273039 A273040 * A273042 A273043 A273044

KEYWORD

nonn

AUTHOR

Jeffrey Shallit, May 13 2016

STATUS

approved

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Last modified October 1 17:45 EDT 2020. Contains 337444 sequences. (Running on oeis4.)