



0, 1, 2, 1, 3, 4, 5, 1, 2, 6, 7, 4, 8, 9, 10, 1, 11, 4, 12, 6, 13, 14, 15, 4, 3, 16, 2, 9, 17, 18, 19, 1, 20, 21, 22, 4, 23, 24, 25, 6, 26, 27, 28, 14, 10, 29, 30, 4, 5, 6, 31, 16, 32, 4, 33, 9, 34, 35, 36, 18, 37, 38, 13, 1, 39, 40, 41, 21, 42, 43, 44, 4, 45, 46, 10, 24, 47, 48, 49, 6, 2, 50, 51, 27, 52, 53, 54, 14, 55, 18, 56, 29, 57, 58, 59, 4, 60, 9, 20, 6
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OFFSET

1,3


COMMENTS

For n > 1, a(n) gives the (onebased) index of the column where n is located in array A284311, or respectively, index of the row where n is in A284457. A008479 gives the other index.


LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = A013928(A007947(n)).
Other identities. For all n >= 0:
If A008683(n) <> 0 [when n is squarefree, A005117], a(n) = A013928(n), otherwise a(n) = a(A285328(n)).
a(A019565(n)) = A064273(n).


PROG

(Scheme, with memoizationmacro definec)
(definec (A285329 n) (if (not (zero? (A008683 n))) (A013928 n) (A285329 (A285328 n))))
(define (A285329 n) (A013928 (A007947 n)))
(Python)
from operator import mul
from sympy import primefactors
from sympy.ntheory.factor_ import core
def a007947(n): return 1 if n<2 else reduce(mul, primefactors(n))
def a013928(n): return sum([1 for i in xrange(1, n) if core(i) == i])
print [a013928(a007947(n)) for n in xrange(1, 101)] # Indranil Ghosh, Apr 18 2017


CROSSREFS

Cf. A008479 (the other index).
Cf. A005117, A007947, A008683, A013928, A019565, A064273, A087207, A285328.
Cf. array A284311 (A284457).
Sequence in context: A325324 A241745 A210040 * A289023 A085985 A285107
Adjacent sequences: A285326 A285327 A285328 * A285330 A285331 A285332


KEYWORD

nonn


AUTHOR

Antti Karttunen, Apr 17 2017


STATUS

approved



