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.

A380823 Semiperimeter of the unique primitive Pythagorean triple whose inradius is A000032(n) and such that its long leg and its hypotenuse are consecutive natural numbers.

Original entry on oeis.org

15, 6, 28, 45, 120, 276, 703, 1770, 4560, 11781, 30628, 79800, 208335, 544446, 1423828, 3725085, 9748320, 25514796, 66787903, 174835650, 457697640, 1198222581, 3136914028, 8212428720, 21500225295, 56288009526, 147363418828, 385801624845, 1010040449160, 2644318093956, 6922911197503
Offset: 0

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Examples

			For n=2, the short leg is A380821(2,1) = 7, the long leg is A380821(2,2) = 24 and the hypotenuse is A380821(2,3) = 25 so the semiperimeter is then a(2) = (7 + 24 + 25)/2 = 28.
		

References

  • Miguel Ángel Pérez García-Ortega, José Manuel Sánchez Muñoz and José Miguel Blanco Casado, El Libro de las Ternas Pitagóricas, Preprint 2025.

Crossrefs

Programs

  • Mathematica
    a=Table[LucasL[n],{n,0,30}];Apply[Join,Map[{(#+1)(2#+1)}&,a]]

Formula

a(n) = (A380821(n,1) + A380821(n,2) + A380821(n,3))/2.
a(n) = (Lucas(n) + 1)*(2*Lucas(n) + 1).
G.f.: (15 - 54*x + 34*x^2 + 35*x^3 - 28*x^4)/((1 - x)*(1 + x)*(1 - 3*x + x^2)*(1 - x - x^2)). - Stefano Spezia, Mar 08 2025

A380824 Area of the unique primitive Pythagorean triple whose inradius is A000032(n) and such that its long leg and its hypotenuse are consecutive natural numbers.

Original entry on oeis.org

30, 6, 84, 180, 840, 3036, 12654, 51330, 214320, 895356, 3767244, 15880200, 67083870, 283656366, 1200287004, 5081015940, 21514542240, 91113336516, 385900503534, 1634538491850, 6923592200280, 29327695892556, 124231206250884, 526244219948880, 2229186359036190, 9442932766091286
Offset: 0

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Author

Keywords

Examples

			For n=2, the short leg is A380821(2,1) = 7 and the long leg is A380821(2,2) = 24 so the area is then a(2) = (7 * 24 )/2 = 84.
		

References

  • Miguel Ángel Pérez García-Ortega, José Manuel Sánchez Muñoz and José Miguel Blanco Casado, El Libro de las Ternas Pitagóricas, Preprint 2025.

Crossrefs

Programs

  • Mathematica
    a=Table[LucasL[n],{n,0,30}];Apply[Join,Map[{#(#+1)(2#+1)}&,a]]

Formula

a(n) = (A380821(n,1) * A380821(n,2))/2.
a(n) = Lucas(n)*(Lucas(n) + 1)*(2*Lucas(n) + 1).

A381721 Sum of the legs of the unique primitive Pythagorean triple whose inradius is A000032(n) and such that its long leg and its hypotenuse are consecutive natural numbers.

Original entry on oeis.org

17, 7, 31, 49, 127, 287, 721, 1799, 4607, 11857, 30751, 79999, 208657, 544967, 1424671, 3726449, 9750527, 25518367, 66793681, 174844999, 457712767, 1198247057, 3136953631, 8212492799, 21500328977, 56288177287, 147363690271, 385802064049, 1010041159807, 2644319243807, 6922913058001, 18124414244999, 47450320478207
Offset: 0

Views

Author

Keywords

Examples

			For n=2, the short leg is A380821(2,1) = 7 and the long leg is A380821(2,2) = 24 so the semiperimeter is then a(2) = 7 + 24 = 31.
		

References

  • Miguel Ángel Pérez García-Ortega, José Manuel Sánchez Muñoz and José Miguel Blanco Casado, El Libro de las Ternas Pitagóricas, Preprint 2025.

Crossrefs

Programs

  • Mathematica
    a=Table[LucasL[n],{n,0,35}];Apply[Join,Map[{2#^2+4#+1}&,a]]

Formula

a(n) = A380821(n,1) + A380821(n,2).
a(n) = 2*(Lucas(n))^2 + 4*Lucas(n) + 1.
G.f.: (x^5-33*x^4+41*x^3+37*x^2-61*x+17)/((x-1)*(x+1)*(x^2-3*x+1)*(x^2+x-1)). - Alois P. Heinz, Jun 16 2025

Extensions

a(19) corrected by Georg Fischer, Jun 16 2025

A386201 Lengths of the long leg in the unique primitive Pythagorean triple whose inradius is A000032(n) and such that its long leg and its hypotenuse are consecutive natural numbers.

Original entry on oeis.org

12, 4, 24, 40, 112, 264, 684, 1740, 4512, 11704, 30504, 79600, 208012, 543924, 1422984, 3723720, 9746112, 25511224, 66782124, 174826300, 457682512, 1198198104, 3136874424, 8212364640, 21500121612, 56287841764, 147363147384, 385801185640, 1010039738512
Offset: 0

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Author

Keywords

Crossrefs

Cf. A000032, A380821 (short legs).

Formula

a(n) = 2 * A000032(n) * (A000032(n) + 1).
Showing 1-4 of 4 results.