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A368625
Characteristic function of non-refactorable numbers (A159973).
1
0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1
OFFSET
1,1
FORMULA
a(n) = ceiling(n/d(n))-floor(n/d(n)), where d(n) is the number of divisors of n (A000005).
a(n) = 1 - A336040(n).
MATHEMATICA
Table[(Ceiling[n/DivisorSigma[0, n]] - Floor[n/DivisorSigma[0, n]]), {n, 100}]
CROSSREFS
Cf. A000005, A033950 (refactorable numbers), A159973, A336040.
Sequence in context: A131736 A373254 A152228 * A086823 A228487 A295306
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Jan 01 2024
STATUS
approved