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!)
A296012 Primes of the form k + k+1 + k+2 +-1 where k, k+1, and k+2 are all composite numbers. 2
79, 101, 103, 149, 151, 167, 191, 193, 227, 229, 257, 277, 281, 283, 347, 349, 353, 359, 367, 373, 401, 431, 433, 439, 461, 463, 479, 509, 557, 563, 607, 613, 617, 619, 641, 643, 647, 653, 659, 661, 709, 733, 739, 743, 761, 797, 821, 823, 857, 859, 863, 887, 907, 911, 967, 971, 977, 983, 1019, 1021 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes p such that floor((p-2)/3) and floor((p-2)/3)+2 are composite. - Robert Israel, Dec 03 2017

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000

EXAMPLE

25 + 26 + 27 + 1 = 79,

33 + 34 + 35 - 1 = 101,

33 + 34 + 35 + 1 = 103, etc.

MAPLE

filter:= proc(n) local k;

  if not isprime(n) then return false fi;

  k:= floor((n-2)/3);

  not isprime(k) and not isprime(k+1) and not isprime(k+2)

end proc:

select(filter, [seq(i, i=5..2000, 2)]); # Robert Israel, Dec 03 2017

MATHEMATICA

Select[Join @@ Map[{{Total@ # - 1, #}, {Total@ # + 1, #}} &, Partition[Range@ 350, 3, 1]], And[PrimeQ@ First@ #, AllTrue[Last@ #, CompositeQ]] &][[All, 1]] (* Michael De Vlieger, Dec 03 2017 *)

PROG

(Python)

from __future__ import division

from sympy import nextprime, isprime

A296012_list, p = [], 2

while len(A296012_list) < 10000:

    k = (p-2)//3

    if not (isprime(k) or isprime(k+2)):

        A296012_list.append(p)

    p = nextprime(p) # Chai Wah Wu, Jan 24 2018

CROSSREFS

Cf. A000045, A136799.

Sequence in context: A285228 A087537 A117840 * A193142 A033250 A139922

Adjacent sequences:  A296009 A296010 A296011 * A296013 A296014 A296015

KEYWORD

nonn

AUTHOR

Martin Michael Musatov, Dec 02 2017

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 September 18 06:40 EDT 2020. Contains 337166 sequences. (Running on oeis4.)