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Search: id:A036689
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| A036689 |
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Product of a prime and previous number. |
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+0
79
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| 2, 6, 20, 42, 110, 156, 272, 342, 506, 812, 930, 1332, 1640, 1806, 2162, 2756, 3422, 3660, 4422, 4970, 5256, 6162, 6806, 7832, 9312, 10100, 10506, 11342, 11772, 12656, 16002, 17030, 18632, 19182, 22052, 22650, 24492, 26406, 27722, 29756, 31862, 32580, 36290, 37056, 38612, 39402, 44310
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Records in A002618 - Artur Jasinski (grafix(AT)csl.pl), Jan 23 2008
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FORMULA
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a(n) = p(n)*[ p(n)-1 ] with p(n) the n-th prime.
a(n)=EulerPhi[Prime[n]^2] = A000010[A001248(n)]
a(n) = Prime[n] EulerPhi[Prime[n]] - Artur Jasinski (grafix(AT)csl.pl), Jan 23 2008
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EXAMPLE
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a(2)=6 because p(2)=3 and p(2)-1=2.
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MATHEMATICA
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Table[Prime[n] EulerPhi[Prime[n]], {n, 1, 100}] - Artur Jasinski (grafix(AT)csl.pl), Jan 23 2008
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CROSSREFS
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Cf. A001248, A002618, A053650, A053192, A053193, A053650.
Cf. A002618.
Sequence in context: A130315 A087150 A087134 this_sequence A139115 A121128 A056820
Adjacent sequences: A036686 A036687 A036688 this_sequence A036690 A036691 A036692
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KEYWORD
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nonn,easy
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AUTHOR
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Felice Russo (felice.russo(AT)katamail.com)
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