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.

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

Alois P. Heinz, Table of n, a(n) for n = 1..5000

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

Adjacent sequences: A209059 A209060 A209061 * A209063 A209064 A209065

Keyword

nonn,base,look

Author

Vladimir Shevelev, Mar 13 2012

Status

approved