A350039 Perimeters of more than one primitive 60-degree integer triangle.
1260, 2520, 2574, 3080, 3740, 3780, 3978, 4620, 4940, 5148, 5720, 5814, 5940, 6435, 6930, 7020, 7280, 7560, 7820, 7866, 7956, 8190, 8550, 8580, 8892, 9044, 10010, 10350, 10395, 10472, 10640, 11628, 11880, 12006, 12240, 12870, 12920, 13050, 13260, 13340, 13680, 13685, 13832, 13860, 13950
Offset: 1
Keywords
Examples
399^2 + 440^2 - 399*440 = 421^2, 56^2 + 615^2 - 56*615 = 589^2 and 399 + 440 + 421 = 56 + 615 + 589 = 1260. So 1260 is a term. 5159^2 + 5904^2 - 5159*5904 = 5569^2, 3344^2 + 7119^2 - 3344*7119 = 6169^2, 1287^2 + 7952^2 - 1287*7952 = 7393^2 and 5159 + 5904 + 5569 = 3344 + 7119 + 6169 = 1287 + 7952 + 7393 = 16632. So 16632 is a term.
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..10000
Programs
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Ruby
def A(n) ary = [] (1..n).each{|i| (i + 1..n).each{|j| if i.gcd(j) == 1 && (i - j) % 3 > 0 x, y, z = j * j, i * j, i * i ary << 2 * x + 5 * y + 2 * z ary << 3 * x + 3 * y end } } ary end p A(100).group_by(&:to_i).select{|k, v| v.size > 1}.keys.sort[0..50]