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A370858
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Let L_1 = (1) and L_2 = (1, 2); for any n > 2, L_n is obtained by inserting one n between each pair of consecutive terms of L_{n-1} coprime to n; a(n) gives the number of terms in L_n.
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2
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1, 2, 3, 4, 7, 8, 15, 24, 43, 56, 111, 132, 263, 420, 723, 1040, 2079, 2472, 4943, 7448, 13091, 19236, 38471, 45884, 86119, 138024, 248459, 359142, 718283, 764160, 1528319, 2605756, 4858899, 7109964, 13809075, 16009784, 32019567, 52524888, 95697787, 125396930
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OFFSET
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1,2
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LINKS
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FORMULA
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a(p) = 2*a(p-1) - 1 for any odd prime number p.
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EXAMPLE
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The first terms, alongside the corresponding lists, are:
n a(n) L n
- ---- ---------------------------------------------
1 1 (1 )
2 2 (1, 2)
3 3 (1, 3, 2)
4 4 (1, 4, 3, 2)
5 7 (1, 5, 4, 5, 3, 5, 2)
6 8 (1, 6, 5, 4, 5, 3, 5, 2)
7 15 (1, 7, 6, 7, 5, 7, 4, 7, 5, 7, 3, 7, 5, 7, 2)
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PROG
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(PARI) See Links section.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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