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Search: id:A130533
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| 0, 0, 2, 6, 13, 9, 2, 19, 2, 19, 2, 3, 4, 37, 8, 43, 47, 47, 53, 2, 6, 59, 61, 8, 71, 6, 79, 2, 5, 83, 89, 2, 3, 12, 101, 107, 4, 3, 3, 2, 11
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OFFSET
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1,3
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COMMENT
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a(n) is the weight of semiprimes. A020639(n) is the weight of natural numbers. A117078(n) is the weight of primes numbers.
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LINKS
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Remi Eismann, Table of n, a(n) for n=1..9999
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EXAMPLE
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For n = 1 we have A001358(n) = 4, A001358(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.
For n = 3 we have A001358(n) = 9, A001358(n+1) = 10; 2 is the smallest k such that 10 - 9 = 1 = (9 mod k), hence a(3) = 2.
For n = 19 we have A001358(n) = 55, A001358(n+1) = 57; 53 is the smallest k such that 57 - 55 = 2 = (55 mod k), hence a(19) = 53.
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CROSSREFS
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Cf. A020639, A117078, A117563, A001223, A118534, A090369, A090368.
Sequence in context: A089415 A161324 A116534 this_sequence A082722 A030416 A006284
Adjacent sequences: A130530 A130531 A130532 this_sequence A130534 A130535 A130536
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KEYWORD
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nonn
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AUTHOR
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Remi Eismann (reismann(AT)free.fr), Aug 16 2007
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