A197881 Number of times n occurs in A197863.

1, 0, 0, 2, 0, 0, 0, 1, 2, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 2

Offset: 1

Author

Franklin T. Adams-Watters, Oct 18 2011

Keywords

• nonn
• easy
• mult

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000
• Index entries for sequences computed from exponents in factorization of n.

Crossrefs

Cf. A197863, A112526.

Programs

Mathematica

f[p_, e_] := Switch[e, 1, 0, 2, 2, , 1]; a[1] = 1; a[n] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Aug 28 2023 *)

PARI

a(n)=my(es=factor(n)[,2]~);prod(k=1,#es,if(es[k]==1,0,if(es[k]==2,2,1)))

Scheme

(define (A197881 n) (cond ((= 1 n) n) (else (* (case (A067029 n) ((1) 0) ((2) 2) (else 1)) (A197881 (A028234 n)))))) ;; Antti Karttunen, Jul 23 2017

Formula

Multiplicative with a(p^e) = 0 if e = 1, 2 if e = 2, and 1 otherwise.

Extensions

More terms from Antti Karttunen, Jul 23 2017