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A114708
a(n) = A114707(n) - A114707(n-1) = the number of distinct primes dividing n but not A114707(n-1).
2
1, 1, 1, 1, 2, 0, 1, 1, 2, 0, 2, 0, 2, 0, 1, 1, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 3, 1, 1, 2, 1, 2, 1, 1, 2, 2, 1, 1, 3, 1, 2, 2, 2, 1, 1, 1, 0, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 0, 2, 1, 1, 1, 1, 2, 1, 2, 1, 1, 2, 2, 2, 3, 1, 2, 1, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 2, 2, 2, 2, 1, 1, 1, 0, 1, 3, 1, 2, 3, 1
OFFSET
2,5
COMMENTS
First occurrence of k=0..8: 7, 2, 6, 30, 330, 4620, 46410, 570570, ..., . - Robert G. Wilson v, Dec 28 2005
EXAMPLE
A114707(11) = 11. Since 2 and 3 are the 2 distinct primes that divide 12 and neither divides 11, a(12) is 2 (and A114707(12) is 2 + A114707(11) = 13).
MATHEMATICA
a[1] = 1; a[n_] := a[n] = a[n - 1] + Length@Complement[First /@ FactorInteger@n, First /@ FactorInteger@a[n - 1]]; b = Array[a, 100]; Drop[b, 1] - Drop[b, -1] (* Robert G. Wilson v, Dec 28 2005 *)
PROG
(PARI) {a=1; for(n=2, 106, print1(d=#setminus(Set(factor(n)[, 1]), Set(factor(a)[, 1])), ", "); a=a+d)} \\ Klaus Brockhaus, Dec 27 2005
CROSSREFS
Cf. A114707.
Sequence in context: A178146 A305435 A350658 * A084927 A333750 A072670
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 26 2005
EXTENSIONS
More terms from Klaus Brockhaus and Robert G. Wilson v, Dec 27 2005
STATUS
approved