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Search: id:A131960
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| A131960 |
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Composite numbers such that the first factor is the relevant exponent of Mersenne prime (the second factor). |
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+0
2
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OFFSET
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1,1
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COMMENT
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What is special about this sequence is that the composite number is a Mangammal composite as defined in A119691.
Perhaps it may not be necessary to run the program from 1 to Eulerphi(MC); it may suffice to run it only up to the exponent.
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FORMULA
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Program for test (in PARI): {p(n)=(3^n-2)/MC} where MC stands for the suspected Mangammal Composite. The program runs from 1 to eulerphi(MC).
a(n)=A000043(i)*A000668(i)=A119691(j) for some pair i,j>=1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 18 2007
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CROSSREFS
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Cf. A123239 & A119691.
Sequence in context: A105986 A129640 A028382 this_sequence A101535 A010086 A110834
Adjacent sequences: A131957 A131958 A131959 this_sequence A131961 A131962 A131963
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KEYWORD
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nonn,bref,uned,obsc,more
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AUTHOR
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A. K. Devaraj (dkandadai(AT)yahoo.com), Aug 02 2007, Aug 06 2007
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