OFFSET
1,1
LINKS
J. K. Andersen, Consecutive Congruent Primes.
EXAMPLE
a(5) = 123229 because this number is the first in a sequence of 5 consecutive primes all of the form 5n + 4.
MATHEMATICA
NextPrime[ n_Integer ] := Module[ {k = n + 1}, While[ ! PrimeQ[ k ], k++ ]; Return[ k ] ]; PrevPrime[ n_Integer ] := Module[ {k = n - 1}, While[ ! PrimeQ[ k ], k-- ]; Return[ k ] ]; p = 0; Do[ a = Table[ -1, {n} ]; k = Max[ 1, p ]; While[ Union[ a ] != {4}, k = NextPrime[ k ]; a = Take[ AppendTo[ a, Mod[ k, 5 ] ], -n ] ]; p = NestList[ PrevPrime, k, n ]; Print[ p[ [ -2 ] ] ]; p = p[ [ -1 ] ], {n, 1, 9} ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Oct 10 2000
EXTENSIONS
Phil Carmody gives a(15)= 4010803176619 in A054681
More terms from Jens Kruse Andersen, Jun 03 2006
a(16)-a(17) from Giovanni Resta, Aug 01 2013
STATUS
approved