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A216944 The least odd prime p for which the n-th prime can be written as 3p + q - 3 for some odd prime q. 1
3, 3, 3, 3, 3, 3, 5, 3, 5, 3, 3, 3, 3, 7, 3, 5, 3, 3, 5, 3, 7, 5, 3, 3, 3, 3, 7, 7, 3, 5, 5, 5, 3, 3, 7, 3, 3, 7, 5, 5, 3, 3, 5, 5, 11, 3, 3, 3, 5, 5, 3, 3, 3, 11, 3, 5, 3, 5, 11, 7, 3, 3, 7, 3, 11, 5, 3, 3, 7, 3, 3, 11, 3, 7, 5, 5, 7, 5, 5, 5, 3, 5, 3, 7, 5, 3, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

5,1

COMMENTS

Conjecture: Any prime >= 11 can be written this way.

LINKS

Robert Israel, Table of n, a(n) for n = 5..10000

EXAMPLE

The corresponding q and prime(n): (5,11), (7,13), (11,17), (13,19), (17,23), (23,29), (19,31), (31,37), (29,41), (37,43), (41,47), (47,53), (53,59), (43,61), (61,67), (67,73), (73,79), (71,83), (83,89), (79,97), (89,101), (97,103), (101,107), (103,109), (107,113), (109,127), (113,131), (131,137), (127,139), (137,149), (139,151), (151,157), (157,163), (149,167), (167,173), (173,179), (163,181), (179,191), (181,193), (191,197), (193,199), (199,211), (211,223), (197,227), (223,229), (227,233), (233,239), (229,241), (239,251), (251,257), (257,263), (263,269), (241,271),  (271,277), (269,281), (277,283), (281,293), (277,307), (293,311), (307,313), (311,317), (313,331), (331,337), (317,347), (337,349), (347,353), (353,359), (349,367), (367,373), (373,379), (353,383), (383,389), (379,397), (389,401), (397,409), (401,419), (409,421), (419,431), (421,433), (433,439), (431,443), (443,449), (439,457), (449,461), (457,463), (461,467), (467,479).

MAPLE

f:= proc(n) local p, q;

  p:= 2;

  while 3*p<n+3 do

    p:= nextprime(p);

    if isprime(n-3*p+3) then return p fi;

  od;

FAIL

end proc:

p:= 7: Res:= NULL:

for i from 1 to 100 do

p:= nextprime(p); Res:= Res, f(p);

od:

Res; # Robert Israel, Mar 08 2018

PROG

(PARI) a(n)=my(r=prime(n)+3); forprime(p=3, r\3-1, if(isprime(r-3*p), return(p))) \\ Charles R Greathouse IV, Dec 07 2014

CROSSREFS

Sequence in context: A081168 A301415 A210509 * A178832 A111233 A210746

Adjacent sequences:  A216941 A216942 A216943 * A216945 A216946 A216947

KEYWORD

nonn

AUTHOR

Marius Coman, Sep 20 2012

EXTENSIONS

New name from Charles R Greathouse IV, Dec 07 2014

Corrected by Charles R Greathouse IV, Dec 07 2014

STATUS

approved

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Last modified August 17 17:04 EDT 2019. Contains 326059 sequences. (Running on oeis4.)