

A284584


a(1) = 0; for n > 1, if n is not squarefree, then a(n) = A057627(n), otherwise a(n) = A013928(n).


3



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

1,3


COMMENTS

Each number n > 0 occurs exactly twice in this sequence, at the positions A005117(1+n) and A013929(n).


LINKS



FORMULA

a(1) = 0; for n > 1, if A008683(n) is 0 [when n is not squarefree], then a(n) = A057627(n), otherwise a(n) = A013928(n).


PROG

(Python)
from sympy import mobius
from sympy.ntheory.factor_ import core
def a057627(n): return n  sum([mobius(k)**2 for k in range(1, n + 1)])
def a013928(n): return sum([1 for i in range(1, n) if core(i) == i])
def a(n):
if n==1: return 0
if core(n)==n: return a013928(n)
else: return a057627(n)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



