OFFSET
1,1
COMMENTS
The term "exactly" means that before the first and after the last primes of chain, the immediate primes are not congruent to 1 modulo 6.
See A057620 for the variant where "exactly" is replaced by "at least". - M. F. Hasler, Sep 03 2016
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..35 (terms < 4*10^14)
J. K. Andersen, Consecutive Congruent Primes.
A. Granville and G. Martin, Prime number races, Amer. Math. Monthly, 113 (No. 1, 2006), 1-33.
MATHEMATICA
pp = Table[{p = Prime[n], Mod[p, 6]}, {n, 10^6}];
sp = Split[pp, Mod[#1[[2]], 6] == Mod[#2[[2]], 6]&];
a[n_] := SelectFirst[sp, Length[#] == n && MatchQ[#, {{_Integer, 1} ..}]& ][[1, 1]];
Table[an = a[n]; Print[n, " ", an]; an, {n, 1, 13}] (* Jean-François Alcover, Nov 21 2018 *)
PROG
(Fortran) c See link in A085515.
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jun 05 2000
EXTENSIONS
Corrected and extended by Reiner Martin, May 19 2001
More terms from Hugo Pfoertner, Jul 31 2003
a(20)>2^31, a(21)=1444257673. - Hugo Pfoertner, Jul 31 2003
More terms from Jens Kruse Andersen, May 30 2006
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 27 2006
STATUS
approved