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A209062
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.
1
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
OFFSET
1,6
LINKS
EXAMPLE
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.
MAPLE
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
CROSSREFS
Cf. A001221.
Sequence in context: A350333 A138010 A206487 * A167204 A376758 A304750
KEYWORD
nonn,base,look
AUTHOR
Vladimir Shevelev, Mar 13 2012
STATUS
approved