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A209062
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Consider all numbers n_1 = n, n_2, ..., n_k obtained from n by permutations of its digits (n_i could begin with 0 except for n_1). Then a(n) is the number of distinct primes dividing at least one from them.
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1
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0, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 3, 2, 3, 3, 2, 2, 2, 3, 2, 3, 2, 2, 3, 3, 3, 2, 3, 3, 3, 2, 2, 2, 3, 3, 3, 2, 3, 3, 2, 3, 3, 3, 2, 3, 2, 3, 3, 3, 2, 3, 3, 3, 3, 2, 4, 3, 4, 3, 3, 2, 3, 3, 2, 4, 3, 3, 3, 3, 3, 2, 2, 2, 3, 3, 3, 2, 4, 2, 2, 2, 3, 3, 3, 4, 3, 4
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OFFSET
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1,6
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LINKS
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EXAMPLE
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Let n=103. We have the following numbers obtained by permutations of its digits: 103, 130, 013, 031, 301, 310. The primes dividing at least one such numbers are 2, 5, 7, 13, 31, 43, 103. Thus a(103) = 7.
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MAPLE
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with(numtheory): with(combinat):
a:= n-> nops({map(x->factorset(parse(cat(x[])))[], permute(convert(n, base, 10)))[]}): seq(a(n), n=1..120); # Alois P. Heinz, Mar 13 2012
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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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