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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A360537 Areas of primitive Heron triangles with two rational medians from the infinite family based on Somos-5 sequences.

Original entry on oeis.org

420, 55440, 23931600, 142334216640, 2137147184560080, 4323341954766548553840, 18705358317240372854759881380, 1333577710124626249998068999458413600, 248363720675646323338068819310182950300884320, 4199805494977793853528867974891927438920668319491840
Offset: 1

Views

Author

Andrey Zabolotskiy, Feb 10 2023

Keywords

Crossrefs

This is a subsequence of A223941.

Programs

  • Mathematica
    t[1|3|4] = 1; t[2] = -1; t[5] = -7;
    s[-2|-1|0|1|2] = 1;
    Do[f[n_] := f[n] = (f[n-1] f[n-4] + f[n-2] f[n-3]) / f[n-5], {f, {t, s}}];
    a[n_] := Abs@Product[f[n] f[n+1] f[n+2]^2 f[n+3] f[n+4], {f, {s, t}}];
    Table[a[n], {n, 10}]

Formula

a(n) = |S(n)*S(n+1)*S(n+2)^2*S(n+3)*S(n+4)*T(n)*T(n+1)*T(n+2)^2*T(n+3)*T(n+4)|, where S(n) = A006721(n+2) and T(n) = A360381(n) [Hone, Eq. (1.21)].

A318575 Areas of primitive Heron triangles with square sides.

Original entry on oeis.org

32918611718880, 284239560530875680
Offset: 1

Views

Author

Max Alekseyev, Aug 29 2018

Keywords

Examples

			a(1) is the area of the Heron triangle with sides 1853^2, 4380^2, 4427^2.
a(2) is the area of the Heron triangle with sides 11789^2, 68104^2, 68595^2.
		

Crossrefs

Extensions

a(1) was found by Stanica et al. (2013).
a(2) was found by Randall L Rathbun (2018).
Showing 1-2 of 2 results.