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Search: id:A121051
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| A121051 |
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Semiprimes which are sums of 4 but no fewer nonzero squares. |
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+0
1
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| 15, 39, 55, 87, 95, 111, 119, 143, 159, 183, 215, 247, 287, 295
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Semiprime analogue of A007522 Primes of form 8n+7. These semiprimes must all be numbers of the form 4^i(8j+7), i >= 0, j >= 0. However, for positive i, 4^i(8j+7) has more than 2 prime factors (with multiplicity). Hence from Legendre's corrolary to Lagrange's Four-Square Theorem, this sequence is precisely Semiprimes of the form 8*k+7.
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CROSSREFS
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A001358 intersect A004215.
Cf. A001358, A004215, A007522.
Sequence in context: A154988 A086096 A055131 this_sequence A139042 A020142 A146696
Adjacent sequences: A121048 A121049 A121050 this_sequence A121052 A121053 A121054
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KEYWORD
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easy,nonn,less
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 08 2006
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