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A333235
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a(n) is the product of indices of unitary prime power divisors of n.
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3
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1, 1, 2, 3, 4, 2, 5, 6, 7, 4, 8, 6, 9, 5, 8, 10, 11, 7, 12, 12, 10, 8, 13, 12, 14, 9, 15, 15, 16, 8, 17, 18, 16, 11, 20, 21, 19, 12, 18, 24, 20, 10, 21, 24, 28, 13, 22, 20, 23, 14, 22, 27, 24, 15, 32, 30, 24, 16, 25, 24, 26, 17, 35, 27, 36, 16, 28, 33, 26, 20
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OFFSET
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1,3
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COMMENTS
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Equivalently: replace each prime power p^e in the prime factorisation of n by its index in A246655. - M. F. Hasler, Jun 16 2021
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LINKS
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FORMULA
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If n = Product (p_j^k_j) then a(n) = Product (A025528(p_j^k_j)).
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EXAMPLE
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MAPLE
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N:= 1000: # for a(1)..a(N)
R:= NULL: p:= 2:
while p < N do
R:= R, seq(p^k, k=1..ilog[p](N));
p:= nextprime(p);
od:
L:= sort([R]):
f:= proc(n) local F, t;
F:= ifactors(n)[2];
mul(ListTools:-BinarySearch(L, t[1]^t[2]), t=F)
end proc:
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MATHEMATICA
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PrimePowerPi[n_] := Sum[Boole[PrimePowerQ[k]], {k, 1, n}]; a[1] = 1; a[n_] := Times @@ (PrimePowerPi[#[[1]]^#[[2]]] & /@ FactorInteger[n]); Table[a[n], {n, 1, 70}]
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PROG
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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