cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A180128 Maximal determinant of an n X n matrix whose elements are a permutation of the first n^2 prime numbers.

Original entry on oeis.org

1, 2, 29, 6640, 4868296, 5725998504, 11305600374272, 35954639671827328
Offset: 0

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Author

Hugo Pfoertner, Aug 11 2010

Keywords

Comments

The terms a(5), a(6), a(7) were found by tabu search, with strong numerical evidence for the optimality of a(7).
A known lower bound for the next term a(8) is 154665569137423060000.
Upper bounds for higher terms can be found by the method described by O. Gasper, H. Pfoertner and M. Sigg, and are given in A180127, e.g., a(8) <= 154715716383037989022.
An improved lower bound is a(8) >= 154671943501236284416, provided in a private communication by Richard Gosiorovsky. - Hugo Pfoertner, Aug 27 2021

Examples

			a(2) = 29:
. 7 3
. 2 5
a(3) = 6640:
. 23 11  5
.  3 17 13
.  7  2 19
a(4) = 4868296:
. 53 11 23 13
. 17 47 29  3
.  7  5 43 37
. 19 31  2 41
a(5) = 5725998504
. 89 41 23  2 53
. 31 97 29 47 11
. 59 13 79 61  7
. 37 19  5 83 67
.  3 43 71 17 73
a(6) = 11305600374272:
. 137  73   7  89  83  13
.  79 139  67  19   3  97
. 101   5 149  61  37  53
.   2 109 103  71 113  11
.  59  29  41  17 131 127
.  23  47  43 151  31 107
a(7) = 35954639671827332:
. 227  71 173  43  83  29  73
. 151 163   5 181   2 103  89
.  31 223 139  61 137  97  13
.  23  47 157 211 109  19 131
. 113   7  67 127 167 199  17
.  53  79 149  37  11 193 179
. 101 107   3  41 191  59 197
		

Crossrefs

Cf. A180127 [upper bounds for a(n)], A085000 [maximal determinants for matrix elements 1, ..., n^2].

Extensions

a(7) corrected, based on private communication from Richard Gosiorovsky by Hugo Pfoertner, Aug 27 2021
a(0)=1 prepended by Alois P. Heinz, Jan 19 2022

A340924 8*a(n) is the maximum possible determinant of a 4 X 4 matrix whose entries are 16 consecutive primes starting with prime(n).

Original entry on oeis.org

608537, 837080, 1062261, 1335740, 1613011, 1834307, 2103606, 2369995, 2621808, 3072665, 3592140, 3891774, 4267302, 4412932, 4443915, 5039601, 5706864, 6673106, 7402050, 8535384, 9378963, 9989532, 10834096, 11530350, 11987568, 13560234, 14289963, 15119412, 15198123
Offset: 1

Views

Author

Hugo Pfoertner, Jan 26 2021

Keywords

Comments

The entries of the matrix are arranged in such a way that the determinant of the matrix is maximized.

Examples

			a(1) = 608537 = A180128(4)/8 with the corresponding matrix shown in A180128.
a(2) = 837080: determinant (
  [59 19 23  7]
  [11 53 37 13]
  [17  5 43 41]
  [29 31  3 47]) = 6696640 = 8*837080.
		

Crossrefs

A340925 16*a(n) is the maximum possible determinant of a 5 X 5 matrix whose entries are 25 consecutive primes starting with prime(n).

Original entry on oeis.org

445934520, 527275650, 606375810, 668638620, 732258072, 860414368, 995563032, 1132837302, 1249798972, 1453587865, 1598993079, 1789976248, 2008319824, 2181193410, 2363922414, 2592209412, 2782039915, 3035727819, 3255326094, 3421333460, 3453338250, 3663999760, 4056944944
Offset: 2

Views

Author

Hugo Pfoertner, Jan 26 2021

Keywords

Comments

The entries of the matrix are arranged in such a way that the determinant of the matrix is maximized.
The special case of the first matrix with determinant A180128(5) = 5725998504 is excluded, since the prime number 2 prevents the otherwise existing divisibility of the determinant by 16.

Examples

			a(2) = 445934520: determinant(
  [73  53  3 79 23]
  [37 101 43  5 47]
  [19  41 89 71 13]
  [11  31 29 61 97]
  [83   7 67 17 59]) = 7134952320 = 16*445934520.
		

Crossrefs

A337160 Primes p such that the 3 X 3 matrix with components (row by row) prime(k+m), 0 <= m <= 8 has zero determinant, where p = prime(k).

Original entry on oeis.org

2213, 4073, 8011, 9041, 15649, 23663, 37483, 38453, 59663, 63487, 65111, 71861, 83557, 97157, 100279, 118801, 129527, 131707, 139291, 163601, 166597, 166799, 180181, 180233, 195691, 203807, 209233, 217201, 227561, 238657, 289139, 309121, 327473
Offset: 1

Views

Author

Jianing Song, Jan 28 2021

Keywords

Comments

Primes arising from A117345.

Examples

			The next 8 primes after 2213 are 2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, and we have det({{2213, 2221, 2237}, {2239, 2243, 2251}, {2267, 2269, 2273}}) = 0, hence 2213 is a term.
		

Crossrefs

Programs

  • PARI
    for(k=1, 35000, M=matrix(3, 3, i, j, prime(k+3*(i-1)+j-1)); if(matdet(M, 1)==0, print1(prime(k), ", ")))

Formula

a(n) = prime(A117345(n)).
Showing 1-4 of 4 results.