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

1,4

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences computed from exponents in factorization of n.

Formula

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

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 *)

Prog

(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

Crossrefs

Cf. A197863, A112526.

Sequence in context: A025086 A035699 A132406 * A332712 A079126 A339086

Adjacent sequences: A197878 A197879 A197880 * A197882 A197883 A197884

Keyword

nonn,easy,mult

Author

Franklin T. Adams-Watters, Oct 18 2011

Extensions

More terms from Antti Karttunen, Jul 23 2017

Status

approved