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A054578 Number of subsequences of {1..n} such that all differences of pairs of terms are distinct (i.e., number of Golomb rulers on {1..n}). 8
1, 3, 6, 12, 21, 35, 56, 90, 139, 215, 316, 462, 667, 961, 1358, 1918, 2665, 3693, 5034, 6844, 9187, 12365, 16416, 21786, 28707, 37721, 49082, 63920, 82639, 106721, 136674, 174894, 222557, 283107, 357726, 451574, 567535, 712855, 890404, 1112080, 1382415 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = A143823(n) - 1. - Carl Najafi, Jan 16 2013

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..60

Index entries for sequences related to Golomb rulers

EXAMPLE

a(4) = 12: [1], [2], [3], [4], [1,2], [1,3], [1,4], [2,3], [2,4], [3,4], [1,2,4], [1,3,4]. - Alois P. Heinz, Jan 16 2013

MAPLE

b:= proc(n, s) local sn, m;

      if n<1 then 1

    else sn:= [s[], n]; m:= nops(sn);

         `if` (m*(m-1)/2 = nops (({seq (seq (sn[i]-sn[j],

           j=i+1..m), i=1..m-1)})), b(n-1, sn), 0) +b(n-1, s)

      fi

    end:

a:= proc(n) a(n):= b(n-1, [n]) +`if` (n=0, -1, a(n-1)) end:

seq(a(n), n=1..30);  # Alois P. Heinz, Jan 16 2013

CROSSREFS

Cf. A003022, A036501.

Sequence in context: A034344 A260640 A203292 * A115855 A234248 A294387

Adjacent sequences:  A054575 A054576 A054577 * A054579 A054580 A054581

KEYWORD

nonn

AUTHOR

John W. Layman, Apr 11 2000

EXTENSIONS

More terms from Carl Najafi, Jan 15 2013

STATUS

approved

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Last modified October 14 15:03 EDT 2019. Contains 328019 sequences. (Running on oeis4.)