The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A319691 a(n) = 1 if n is either 1 or divisible only by primes congruent to 1 mod 3, 0 otherwise. 3
 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1 LINKS Antti Karttunen, Table of n, a(n) for n = 1..65537 FORMULA a(n) = A319690(n) mod 2. Fully multiplicative with a(p) = 1 if p is a prime of the form 3k+1, otherwise a(p) = 0. MATHEMATICA Table[If[AllTrue[FactorInteger[n][[All, 1]], Mod[#, 3]==1&], 1, 0], {n, 120}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 26 2020 *) PROG (PARI) A319691(n) = factorback(apply(p -> ((p%3)%2), factor(n)[, 1])); CROSSREFS Characteristic function of A004611. Cf. A319690. Sequence in context: A015989 A267417 A014189 * A079979 A288711 A347312 Adjacent sequences:  A319688 A319689 A319690 * A319692 A319693 A319694 KEYWORD nonn,mult AUTHOR Antti Karttunen, Oct 04 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 24 09:10 EDT 2021. Contains 347630 sequences. (Running on oeis4.)