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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A091113 Nonprimes of the form 4*k+1. 13
1, 9, 21, 25, 33, 45, 49, 57, 65, 69, 77, 81, 85, 93, 105, 117, 121, 125, 129, 133, 141, 145, 153, 161, 165, 169, 177, 185, 189, 201, 205, 209, 213, 217, 221, 225, 237, 245, 249, 253, 261, 265, 273, 285, 289, 297, 301, 305, 309, 321, 325, 329, 333, 341, 345 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Muniru A Asiru, Table of n, a(n) for n = 1..10000

MAPLE

A091113 := proc(n)

    option remember;

    if n =1 then

        1;

    else

        for a from procname(n-1)+4 by 4 do

            if not isprime(a) then

                return a;

            end if;

        end do:

    end if;

end proc:

seq(A091113(n), n=1..100) ; # R. J. Mathar, Aug 29 2018

MATHEMATICA

Do[If[ !PrimeQ[n]&&Equal[Mod[n, 4], 1], Print[n]], {n, 1, 1000}]

Select[4*Range[0, 100]+1, !PrimeQ[#]&] (* Harvey P. Dale, Oct 28 2017 *)

PROG

(GAP) Filtered(List([0..100], k->4*k+1), n->not IsPrime(n)); # Muniru A Asiru, Mar 10 2019

(MAGMA) [n: n in [1..350] | IsIntegral((n-1)/4) and not IsPrime(n)]; // G. C. Greubel, Mar 10 2019

(Sage) [n for n in (1..350) if ((n-1)/4).is_integer() and not is_prime(n)] # G. C. Greubel, Mar 10 2019

(PARI) isok(n) = !isprime(n) && !((n-1) % 4); \\ Michel Marcus, Mar 11 2019

CROSSREFS

Cf. A091236, A014076.

Subsequence of A016813 (4*n+1).

Sequence in context: A327756 A210251 A143791 * A188159 A272600 A327862

Adjacent sequences:  A091110 A091111 A091112 * A091114 A091115 A091116

KEYWORD

nonn

AUTHOR

Labos Elemer, Feb 24 2004

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 5 10:20 EDT 2020. Contains 333239 sequences. (Running on oeis4.)