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A069248 Number of positive divisors of n themselves divisible by largest prime that divides n. 0
0, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 2, 2, 4, 1, 4, 1, 3, 2, 2, 1, 4, 2, 2, 3, 3, 1, 4, 1, 5, 2, 2, 2, 6, 1, 2, 2, 4, 1, 4, 1, 3, 3, 2, 1, 5, 2, 4, 2, 3, 1, 6, 2, 4, 2, 2, 1, 6, 1, 2, 3, 6, 2, 4, 1, 3, 2, 4, 1, 8, 1, 2, 4, 3, 2, 4, 1, 5, 4, 2, 1, 6, 2, 2, 2, 4, 1, 6, 2, 3, 2, 2, 2, 6, 1, 4, 3, 6 (list; graph; refs; listen; history; internal format)
OFFSET

1,4

FORMULA

d(n) E_n/(E_n + 1), where d(n) is the number of positive divisors of n and E_n is the exponent of the largest prime to divide n in the prime factorization of n.

EXAMPLE

The divisors of 12 which are themselves divisible by 3 (the largest prime dividing 12) are 3, 6 and 12. So the 12th term is 3.

CROSSREFS

Sequence in context: A086436 A001222 A098893 * A008481 A127669 A056692

Adjacent sequences:  A069245 A069246 A069247 * A069249 A069250 A069251

KEYWORD

nonn

AUTHOR

Leroy Quet, Apr 08 2002

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Last modified February 15 15:20 EST 2012. Contains 205823 sequences.