A325684 Number of minimal complete rulers of length n.

1, 1, 1, 2, 3, 4, 5, 12, 12, 24, 40, 46, 92, 133, 192, 308, 546, 710, 1108, 1754, 2726, 3878, 5928, 9260, 14238, 20502, 30812, 48378, 72232, 105744, 160308, 241592, 362348, 540362, 797750, 1183984, 1786714

Offset

0,4

Comments

A complete ruler of length n is a subset of {0..n} containing 0 and n and such that the differences of distinct terms (up to sign) cover an initial interval of positive integers.

Also the number of maximal (most coarse) compositions of n whose consecutive subsequence-sums cover an initial interval of positive integers.

Links

Table of n, a(n) for n=0..36.

Example

The a(1) = 1 through a(7) = 12 rulers:
  {0,1}  {0,1,2}  {0,1,3}  {0,1,2,4}  {0,1,2,5}  {0,1,4,6}    {0,1,2,3,7}
                  {0,2,3}  {0,1,3,4}  {0,1,3,5}  {0,2,5,6}    {0,1,2,4,7}
                           {0,2,3,4}  {0,2,4,5}  {0,1,2,3,6}  {0,1,2,5,7}
                                      {0,3,4,5}  {0,1,3,5,6}  {0,1,3,5,7}
                                                 {0,3,4,5,6}  {0,1,3,6,7}
                                                              {0,1,4,5,7}
                                                              {0,1,4,6,7}
                                                              {0,2,3,6,7}
                                                              {0,2,4,6,7}
                                                              {0,2,5,6,7}
                                                              {0,3,5,6,7}
                                                              {0,4,5,6,7}
The a(1) = 1 through a(9) = 24 compositions:
  (1)  (11)  (12)  (112)  (113)  (132)   (1114)  (1133)   (1143)
             (21)  (121)  (122)  (231)   (1123)  (1241)   (1332)
                   (211)  (221)  (1113)  (1132)  (1322)   (2331)
                          (311)  (1221)  (1222)  (1412)   (3411)
                                 (3111)  (1231)  (1421)   (11115)
                                         (1312)  (2141)   (11124)
                                         (1321)  (2231)   (11142)
                                         (2131)  (3311)   (11241)
                                         (2221)  (11114)  (11322)
                                         (2311)  (11132)  (12141)
                                         (3211)  (23111)  (12222)
                                         (4111)  (41111)  (12231)
                                                          (12312)
                                                          (13221)
                                                          (14112)
                                                          (14121)
                                                          (14211)
                                                          (21141)
                                                          (21321)
                                                          (22221)
                                                          (22311)
                                                          (24111)
                                                          (42111)
                                                          (51111)

Mathematica

fasmin[y_]:=Complement[y, Union@@Table[Union[s, #]&/@Rest[Subsets[Complement[Union@@y, s]]], {s, y}]];
Table[Length[fasmin[Accumulate/@Select[Join@@Permutations/@IntegerPartitions[n], SubsetQ[ReplaceList[#, {___, s__, ___}:>Plus[s]], Range[n]]&]]], {n, 0, 15}]

Crossrefs

Cf. A000079, A103295, A126796, A143823, A169942, A325677, A325683, A325685.

Sequence in context: A193679 A066574 A240304 * A339453 A281597 A039007

Adjacent sequences: A325681 A325682 A325683 * A325685 A325686 A325687

Keyword

nonn,more

Author

Gus Wiseman, May 13 2019

Extensions

a(16)-a(36) from Fausto A. C. Cariboni, Feb 27 2022

Status

approved