login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A222565 Primes that are the largest anti-divisor of primes. 5
2, 3, 5, 7, 11, 13, 19, 29, 31, 41, 47, 53, 59, 67, 71, 73, 101, 109, 127, 131, 149, 151, 167, 179, 181, 211, 233, 239, 281, 293, 307, 311, 347, 349, 379, 401, 409, 421, 431, 439, 449, 461, 467, 479, 541, 547, 569, 571, 587, 607, 613, 619, 631, 647, 661, 673, 701 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A066272 for definition of anti-divisor.

Primes p such that 2p + largest anti-divisor of 2p is also prime: 2, 5, 7, 11, 13, 29, 31, 41, 47, 59, 67, 79, 83, 101, 137, 139, 151, 157, 167, 173, 193, 223, 227, 239, 257,...

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

FORMULA

2 together with primes of the form 4k+1 such that 6k+1 is prime, together with primes of the form 4k+3 such that 6k+5 is prime. - Charles R Greathouse IV, Feb 27 2013

EXAMPLE

The prime 19 is here because it is largest anti-divisor of prime 29.

MAPLE

A222565 := proc(q) local a, b, k, n;

for n from 2 to q do a:={}; b:=ithprime(n);

  for k from 2 to b-1 do if abs((b mod k)-k/2)<1 then a:=a union {k}; fi; od;

  k:=nops(a); b:=sort([op(a)]); if isprime(b[k]) then print(b[k]); fi;

od; end:

A222565(1000000); # Paolo P. Lava, Mar 08 2013

PROG

(PARI) is(n)=isprime(n)&&isprime(bitor((3*n-1)\2, 1)) \\ Charles R Greathouse IV, Feb 27 2013

CROSSREFS

Cf. A066481.

Sequence in context: A237827 A114111 A155108 * A113188 A242738 A079153

Adjacent sequences:  A222562 A222563 A222564 * A222566 A222567 A222568

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Feb 25 2013

EXTENSIONS

Missing terms a(9), a(21), a(28), a(29) added by Charles R Greathouse IV, Feb 27 2013

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 July 15 14:33 EDT 2019. Contains 325031 sequences. (Running on oeis4.)