A070115 - OEIS

A070115

Numbers m such that [A070080(m), A070081(m), A070082(m)] is an isosceles integer triangle.

1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, 15, 16, 18, 19, 22, 23, 24, 26, 27, 28, 31, 32, 34, 35, 38, 39, 40, 43, 46, 47, 48, 51, 52, 54, 55, 58, 61, 63, 64, 65, 68, 71, 72, 73, 76, 81, 82, 84, 85, 88, 91, 93, 94, 95, 98, 103, 104, 107, 108

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

OFFSET

1,2

LINKS

Jean-François Alcover, Table of n, a(n) for n = 1..365

Reinhard Zumkeller, Integer-sided triangles

EXAMPLE

26 is a term because [A070080(26), A070081(26), A070082(26)] = [4=4<6].

MATHEMATICA

m = 55 (* max perimeter *);

sides[per_] := Select[Reverse /@ IntegerPartitions[per, {3}, Range[ Ceiling[per/2]]], #[[1]] < per/2 && #[[2]] < per/2 && #[[3]] < per/2 &];

triangles = DeleteCases[Table[sides[per], {per, 3, m}], {}] // Flatten[#, 1]& // SortBy[Total[#] m^3 + #[[1]] m^2 + #[[2]] m + #[[1]] &];

Position[triangles, {a_, a_, b_} | {a_, b_, b_}] // Flatten (* Jean-François Alcover, Oct 12 2021 *)

CROSSREFS

Cf. A059169, A070116, A070117, A070124, A070125, A070126, A070133, A070134, A070135.

Sequence in context: A187226 A026470 A014133 * A073571 A328242 A294295

Adjacent sequences: A070112 A070113 A070114 * A070116 A070117 A070118

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, May 05 2002

STATUS

approved