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.

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A179838 Triangle T(n,k) read by rows: the coefficient [x^k] of the product_{s=1..n} (x+64*cos(s*Pi/(2n+1))^6), 0<=k<=n.

Original entry on oeis.org

1, 1, 1, 1, 18, 1, 1, 129, 38, 1, 1, 571, 627, 58, 1, 1, 1884, 6212, 1525, 78, 1, 1, 5103, 43123, 24576, 2823, 98, 1, 1, 11998, 230241, 277500, 63660, 4521, 118, 1, 1, 25362, 1005267, 2379096, 1014681, 131464, 6619, 138, 1, 1, 49347, 3744753, 16359996, 12301986, 2724266, 235988, 9117, 158, 1
Offset: 0

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Author

R. J. Mathar, Jan 10 2011

Keywords

Comments

Polynomial coefficients of H_n^(3)(x) by Bostan et al.

Examples

			1
1 1
1 18 1
1 129 38 1
1 571 627 58 1
1 1884 6212 1525 78 1
1 5103 43123 24576 2823 98 1
1 11998 230241 277500 63660 4521 118 1
1 25362 1005267 2379096 1014681 131464 6619 138 1
1 49347 3744753 16359996 12301986 2724266 235988 9117 158 1
		

Crossrefs

Column k=1 is A244879.
Cf. A179837.

Programs

  • PARI
    my(x='x+O('x^10)); concat(apply(p->Vecrev(p), Vec(Ser((1-x)*((x-1)^6 - t*x^2*(x+3)*(3*x+1))/(t^2*x^4-t*x*(x^4+14*x^3+34*x^2+14*x+1)*(x-1)^2+(x-1)^8))))) \\ Gheorghe Coserea, Apr 20 2017

Formula

A(x;t) = Sum_{n>=0} P_n(t)*x^n = (1-x)*((x-1)^6 - t*x^2*(x+3)*(3*x+1))/(t^2*x^4-t*x*(x^4+14*x^3+34*x^2+14*x+1)*(x-1)^2+(x-1)^8), where P_n(t) = Sum_{k=0..n} T(n,k)*t^k. - Gheorghe Coserea, Apr 20 2017

Extensions

Terms a(38) and beyond from Andrew Howroyd, Apr 13 2021

A380964 Perimeter-magic hexagons of order 3 with magic sum n.

Original entry on oeis.org

9, 48, 150, 494, 1202, 2542, 4635, 9738, 14943, 25917, 41196, 62518, 89657, 139743, 185114, 264483, 363291, 485411, 630099, 862106, 1067459, 1391011, 1771817, 2210554, 2712337, 3461467, 4115434, 5073010, 6165577, 7387876, 8748214, 10655591, 12333486, 14679050, 17281206
Offset: 17

Views

Author

Derek Holton and Alex Holton, Feb 09 2025

Keywords

Comments

Each side of the hexagon has 3 integers (=the order), 2 of them shared by adjacent sides. All 12 integers on the vertices must be distinct. Solutions obtained by rotations around the 6-fold axis or flips are considered the same/equivalent (bracelet symmetry).
A244879(n-3) counts the perimeter-magic hexagons of order 3 if the 12 integers do not need to be distinct and if solutions by rotations/reflections are considered distinct. - R. J. Mathar, Mar 10 2025

Examples

			For magic sum 17, a(17) = 9. One of the hexagons is   5   9   3
                                                    10          8
                                                   2             6
                                                    14          7
                                                      1   12   4
		

Crossrefs

Cf. A380853 (triangles), A380962 (squares), A380963 (pentagons).

Extensions

More terms from Bert Dobbelaere, Mar 15 2025
Previous Showing 11-12 of 12 results.