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A285329 a(n) = A013928(A007947(n)). 7
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For n > 1, a(n) gives the (one-based) 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 memoization-macro 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

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Last modified December 5 20:54 EST 2019. Contains 329779 sequences. (Running on oeis4.)