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A336942
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Number of strict chains of divisors in A130091 (numbers with distinct prime multiplicities) starting with the superprimorial A006939(n) and ending with 1.
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7
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OFFSET
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0,3
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LINKS
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FORMULA
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EXAMPLE
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The a(0) = 1 through a(2) = 5 chains:
{1} {2,1} {12,1}
{12,2,1}
{12,3,1}
{12,4,1}
{12,4,2,1}
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MATHEMATICA
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chern[n_]:=Product[Prime[i]^(n-i+1), {i, n}];
chnstr[n_]:=If[n==1, 1, Sum[chnstr[d], {d, Select[Most[Divisors[n]], UnsameQ@@Last/@FactorInteger[#]&]}]];
Table[chnstr[chern[n]], {n, 0, 3}]
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CROSSREFS
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A337075 is the version for factorials.
A074206 counts chains of divisors from n to 1.
A130091 lists numbers with distinct prime multiplicities.
A181796 counts divisors with distinct prime multiplicities.
A327498 gives the maximum divisor with distinct prime multiplicities.
Cf. A000005, A001055, A002033, A032741, A067824, A124010, A167865, A336419, A336420, A336500, A336568.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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