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A101040 If n has one or two prime-factors then 1 else 0. 8
0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(A033942(n))=0; for n>1: a(A037143(n))=1;

a(A000040(n))=1; a(A001358(n))=1;

A101041(n) = Sum(a(k): 1<=k<=n) + 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) = A010051(n)+A064911(n) = 0^floor(A001222(n)/3)-0^(n-1).

a(1) = 0; for n > 1, a(n) = A063524(A032742(A032742(n))). - Antti Karttunen, Nov 23 2017

PROG

(Scheme) (define (A101040 n) (if (= 1 n) 0 (A063524 (A032742 (A032742 n))))) ;; Antti Karttunen, Nov 23 2017

CROSSREFS

Characteristic function of A037143 (without its initial term 1).

Sequence in context: A075897 A135947 A211487 * A306453 A175629 A109720

Adjacent sequences:  A101037 A101038 A101039 * A101041 A101042 A101043

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 28 2004

STATUS

approved

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Last modified September 24 07:28 EDT 2020. Contains 337317 sequences. (Running on oeis4.)