A257785 Numbers that are Belgian-k for exactly one k.

0, 47, 49, 59, 65, 68, 76, 78, 79, 85, 87, 89, 95, 96, 98, 167, 177, 187, 193, 194, 239, 267, 268, 269, 286, 287, 293, 298, 299, 338, 349, 359, 367, 379, 394, 397, 398, 418, 437, 438, 458, 478, 479, 492, 497, 498, 499, 507, 528, 529, 536, 547, 548, 560, 568

Offset: 1

Author

Reinhard Zumkeller, May 08 2015

Keywords

• nonn

Comments

See A106039 for definition of Belgian-k numbers;

A257773(a(n)) = 1;

A257778(a(n)) = A257779(a(n)).

Examples

			Let B(n) = A257778(a(n)), the singleton of a(n)-th row in A257770:
.   n |  a(n) | B(n)        n |  a(n) | B(n)         n |  a(n) | B(n)
.  ---+-------+-----     -----+-------+-----     ------+-------+-----
.   1 |     0 |   0       100 |   763 |   4       1000 |  6702 |   6
.   2 |    47 |   3       101 |   766 |   6       1001 |  6706 |   5
.   3 |    49 |   6       102 |   768 |   5       1002 |  6709 |   8
.   4 |    59 |   3       103 |   769 |   8       1003 |  6719 |   3
.   5 |    65 |   4       104 |   779 |   6       1004 |  6725 |   5
.   6 |    68 |   6       105 |   781 |   6       1005 |  6728 |   6
.   7 |    76 |   4       106 |   785 |   5       1006 |  6730 |   4
.   8 |    78 |   3       107 |   787 |   2       1007 |  6736 |   4
.   9 |    79 |   8       108 |   788 |   6       1008 |  6742 |   3
.  10 |    85 |   7       109 |   789 |   6       1009 |  6747 |   3
.  11 |    87 |   4       110 |   790 |   6       1010 |  6748 |   6
.  12 |    89 |   4       111 |   793 |   7       1011 |  6752 |   6
.  13 |    95 |   2       112 |   794 |   7       1012 |  6753 |   6
.  14 |    96 |   6       113 |   795 |   2       1013 |  6755 |   3
.  15 |    98 |   4       114 |   796 |   4       1014 |  6756 |   6
.  16 |   167 |   6       115 |   797 |   8       1015 |  6758 |   6
.  17 |   177 |   4       116 |   798 |   6       1016 |  6766 |   3
.  18 |   187 |   2       117 |   799 |   8       1017 |  6768 |   5
.  19 |   193 |   1       118 |   805 |   4       1018 |  6770 |   4
.  20 |   194 |   2       119 |   807 |   4       1019 |  6772 |   5  .
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A257770, A257773, A007088, A257778, A257779.

Programs

Haskell

a257785 n = a257785_list !! (n-1)
a257785_list = filter ((== 1) . a257773) [0..]