OFFSET
1,1
COMMENTS
From Rémi Eismann, May 14 2006; May 04 2007: (Start)
Also primes for which k is equal to 5 in A117078. Examples: prime(9) = prime(8) + (prime(8) mod 5) = 19 + (19 mod 5)=23; prime(23) = prime(22) + (prime(22) mod 5) = 79 + (79 mod 5)=83; prime(1359) = prime(1358) + (prime(1358) mod 5) = 11239+ (11239 mod 5)=11243.
The prime numbers in this sequence are of the form (10i-1) with i=(level(n)+1)/2, level(n) defined in A117563.
Consider A117078: a(n) = smallest k such that prime(n+1) = prime(n) + (prime(n) mod k), or 0 if no such k exists. Sequence gives values of prime(n) for which k=5. (End)
p is the lesser member of cousin primes (p,p+4) such that p == 9 (mod 10). - Muniru A Asiru, Jul 03 2017
LINKS
Remi Eismann, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Cousin Primes
MATHEMATICA
Prime[ Select[ Range[1000], Prime[ # ] + 4 == Prime[ # + 1] && Mod[ Prime[ # ], 10] == 9 & ]]
Transpose[Select[Partition[Prime[Range[820]], 2, 1], Last[#]-First[#] == 4 && Mod[ First[ #], 10]==9&]][[1]] (* Harvey P. Dale, Oct 20 2011 *)
PROG
(PARI) is(n)=n%30==19 && isprime(n+4) && isprime(n) \\ Charles R Greathouse IV, Jul 12 2017
(PARI) list(lim)=my(v=List(), p=19); forprime(q=23, lim+4, if(q-p==4 && p%30==19, listput(v, p)); p=q); Vec(v) \\ Charles R Greathouse IV, Jul 12 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Sep 30 2002
EXTENSIONS
Edited by Robert G. Wilson v and N. J. A. Sloane, Oct 03 2002
Entry revised by N. J. A. Sloane, Feb 24 2007
STATUS
approved