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A280710 Characteristic function of squarefree semiprimes. 8
0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Index entries for sequences computed from exponents in factorization of n

FORMULA

a(n) = floor(Omega(n)*mu(n)^2/2)*floor(2*mu(n)^2/Omega(n)) for n>1 with a(1) = 0 where Omega(n) = A001222(n) and mu(n) = A008683(n).

a(n) = A008966(n)*A064911(n). - Felix Fröhlich, Jan 07 2017

MAPLE

with(numtheory): A280710:=n->`if`(bigomega(n)*mobius(n)^2 = 2, 1, 0): seq(A280710(n), n=1..100);

MATHEMATICA

Table[If[PrimeOmega[n] MoebiusMu[n]^2 == 2, 1, 0], {n, 1, 90}] (* Indranil Ghosh, Mar 10 2017 *)

PROG

(PARI) a(n) = bigomega(n)==2*issquarefree(n) \\ Felix Fröhlich, Jan 07 2017

CROSSREFS

Cf. A001222, A006881, A008683, A008966, A064911.

Sequence in context: A011673 A104853 A231600 * A323170 A215480 A143731

Adjacent sequences:  A280707 A280708 A280709 * A280711 A280712 A280713

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Jan 07 2017

EXTENSIONS

More terms from Antti Karttunen, Nov 20 2017

STATUS

approved

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Last modified August 14 13:16 EDT 2020. Contains 336480 sequences. (Running on oeis4.)