OFFSET
1,1
COMMENTS
Let P1,P2,..,P8 be any 8 consecutive primes. The sequence consists of those values of P3 for which P2-P1 > 2, P4-P3 = 2, P6-P5= 2 and P8-P7 > 2.
REFERENCES
Posting to Number Theory List (NMBRTHRY(AT)LISTSERV.NODAK.EDU), Nov. 19 1998.
LINKS
Sebastian Petzelberger, Table of n, a(n) for n = 1..10000
G. L. Honaker, Jr. and Chris Caldwell, 10000...01521 (100-digits)
Hugo Pfoertner, FORTRAN program: Consecutive pairs of twin primes.
FORMULA
a(10)=2111, a(10^2)=77261, a(10^3)=1603697, a(10^4)=27397631, a(10^5)=435140477, a(10^6)=6391490657. - M. F. Hasler, May 04 2015
EXAMPLE
89, 97, 101, 103, 107, 109, 113, 127: 97-89 > 2, 103-101 = 2, 109-107 = 2, 127-113 > 2.
MATHEMATICA
Select[Prime@ Range@ 2100, And[NextPrime[#, -1] - NextPrime[#, -2] > 2, NextPrime@ # - # == 2, NextPrime[#, 3] - NextPrime[#, 2] == 2, NextPrime[#, 5] - NextPrime[#, 4] > 2] &] (* Michael De Vlieger, Apr 25 2015 *)
PROG
(PARI) a(n)={L=vector(7); forprime(p=o=1, , L=concat(L[2..7], -o+o=p); L[3]==2&&L[5]==2&&L[1]>2&&L[2]>2&&L[4]>2&&L[6]>2&&L[7]>2&&!n--&&return(p-sum(i=3, 7, L[i])))} \\ M. F. Hasler, May 04 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Randall L Rathbun, Nov 30 1998
EXTENSIONS
Edited by Hugo Pfoertner, Oct 15 2003
Offset corrected by Arkadiusz Wesolowski, May 06 2012
Double-checked up to a(10^4)=27397631 by M. F. Hasler, May 04 2015
STATUS
approved