A342467 a(n) is the number of n-th order magic triangles.

0, 4, 18, 700, 13123, 316424, 7317145, 176476738, 4279366371, 105120240434, 2601357956367, 64849677951376, 1626044879952455, 40982402321764598, 1037488276154487718, 26367388486630772580, 672435297411296168999, 17201751655032281185462, 441261082844158431491567, 11347558713675700941850950

Offset

2,2

Comments

The Trotter reference gives the value 1356 = 76 * 18 for a(5), which is incorrect since 76 is the number of corner groupings and 18 is the maximum number of solutions in any grouping. - Andrew Howroyd, Feb 05 2022

Links

Table of n, a(n) for n=2..21.

Andrew Howroyd, PARI Program, Feb 2022.

Terrel Trotter, Normal Magic Triangles of Order n, Journal of Recreational Mathematics Vol. 5, No. 1, 1972, pp. 28-32.

Terrel Trotter, Perimeter-Magic Polygons, Journal of Recreational Mathematics Vol. 7, No. 1, 1974, pp. 14-20.

Formula

a(n) < A351223(n). - Stefano Spezia, Feb 05 2022

Prog

(PARI) \\ See Links.

Crossrefs

Row sums of A342384.

Cf. A016777, A179805, A285009, A341740, A351223.

Sequence in context: A383772 A295223 A173222 * A367533 A156491 A384595

Adjacent sequences: A342464 A342465 A342466 * A342468 A342469 A342470

Keyword

nonn

Author

Stefano Spezia, Mar 13 2021

Extensions

a(5) corrected by Andrew Howroyd and Stefano Spezia, Feb 05 2022

a(6)-a(10) from Andrew Howroyd, Feb 05 2022

a(11)-a(21) from Bert Dobbelaere, Nov 18 2025

Status

approved