A375474 - OEIS

A375474

Numbers k such that k is the area of a rational isosceles triangle.

3, 7, 10, 11, 12, 14, 15, 17, 19, 23, 26, 27, 28, 30, 31, 35, 39, 40, 42, 43, 44, 46, 47, 48, 51, 55, 56, 58, 59, 60, 62, 63, 67, 68, 69, 71, 74, 75, 76, 77, 78, 79, 82, 83, 87, 90, 91, 92, 94, 95, 97, 99, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 115, 119, 120, 122, 123

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

All the integer areas of rational isosceles triangles can be obtained by multiplying a squarefree area of a rational isosceles triangle A375017 by a positive square number A000290.

LINKS

Frank M Jackson, Table of n, a(n) for n = 1..2895

EXAMPLE

12 is the area of an isosceles triangle with sides (5, 5, 6).

40 is the area of an isosceles triangle with sides (12, 82/3, 82/3).

MATHEMATICA

lst=Last/@ReadList["https://oeis.org/A375017/b375017.txt", {Number, Number}]; dmax=75; Select[(Sort@Flatten@Table[Table[lst[[n]]*d^2, {d, 1, dmax}], {n, 1, Length@lst}]), #<=140 &]

CROSSREFS

Cf. A000290, A375017.

Sequence in context: A144399 A310176 A138935 * A030325 A095947 A335488

Adjacent sequences: A375471 A375472 A375473 * A375475 A375476 A375477

KEYWORD

nonn

AUTHOR

Frank M Jackson, Aug 17 2024

STATUS

approved