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A070092
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Number of isosceles integer triangles with perimeter n and prime side lengths.
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5
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0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 0, 1, 0, 1, 0, 0, 1, 2, 0, 2, 1, 2, 0, 1, 0, 2, 0, 1, 1, 2, 0, 3, 1, 3, 0, 2, 0, 3, 0, 1, 1, 3, 0, 3, 0, 2, 0, 1, 0, 3, 0, 1, 1, 2, 0, 3, 1, 4, 0, 2, 0, 4, 0, 1, 0, 1, 0, 4, 1, 3, 0, 2, 0, 3, 0, 1, 1, 3, 0, 4, 1, 4, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,17
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COMMENTS
| a(n)=A070088(n)-A070090(n).
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LINKS
| R. Zumkeller, Integer-sided triangles
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EXAMPLE
| For n=17 there are A005044(17)=8 integer triangles: [1,8,8], [2,7,8], [3,6,8], [3,7,7], [4,5,8], [4,6,7], [5,5,7] and [5,6,6]: four are isosceles: [1<8=8], [3<7=7], [5=5<7] and [5<6=6], but only two of them consist of primes, therefore a(17)=2.
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CROSSREFS
| Cf. A070080, A070081, A070082, A059169, A070100, A070108, A070117.
Sequence in context: A060951 A115525 A065717 * A123671 A191261 A179010
Adjacent sequences: A070089 A070090 A070091 * A070093 A070094 A070095
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 05 2002
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