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A158901
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A051731 * (1, 1, 2, 3, 4, 5, ...).
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2
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1, 2, 3, 5, 5, 9, 7, 12, 11, 15, 11, 23, 13, 21, 21, 27, 17, 34, 19, 37, 29, 33, 23, 53, 29, 39, 37, 51, 29, 65, 31, 58, 45, 51, 45, 83, 37, 57, 53, 83, 41, 89, 43, 79, 73, 69, 47, 115, 55, 88, 69, 93, 53, 113, 69, 113, 77, 87, 59, 157, 61, 93, 99, 121, 81, 137, 67, 121, 93, 137
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OFFSET
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1,2
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COMMENTS
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a(n) = prime(n) if n is prime but nonprime n's can also have prime a(n).
Equals left border of triangle A158902.
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LINKS
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FORMULA
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A051731 * [1, 1, 2, 3, 4, 5, ...] = inverse Mobius transform of [1, 1, 2, 3, 4, ...].
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EXAMPLE
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a(4) = 5 = (1, 1, 0, 1) dot (1, 1, 2, 3) = (1 + 1 + 0 + 3); where (1, 1, 0, 1) = row 4 of triangle A051731.
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MAPLE
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L := [1, seq(n, n=1..100)] ; read("transforms"); MOBIUSi(L) ; # R. J. Mathar, Apr 02 2009
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PROG
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(PARI) a(n) = sigma(n) - numdiv(n) + 1; \\ Michel Marcus, Sep 14 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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