

A053673


Least number > 1 coprime to n, n+1, n+2, n+3 and n+4.


8



7, 7, 11, 11, 11, 11, 13, 7, 7, 17, 17, 11, 11, 11, 7, 7, 11, 13, 13, 13, 13, 7, 7, 11, 11, 11, 11, 11, 7, 7, 13, 13, 13, 11, 11, 7, 7, 11, 11, 13, 13, 13, 7, 7, 11, 11, 11, 11, 11, 7, 7, 17, 13, 13, 13, 11, 7, 7, 11, 11, 11, 17, 17, 7, 7, 13, 11, 11, 11, 11, 7, 7, 13, 17, 17, 17, 17
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OFFSET

1,1


COMMENTS

Least prime that does not divide n(n+1)(n+2)(n+3)(n+4).
All terms are primes >= 7.
First occurrences of the first few values:
a(1) = 7, a(3) = 11, a(7) = 13, a(10) = 17, a(117) = 19, a(152) = 23, a(1309) = 29, a(986) = 31, a(1767) = 37, a(203201) = 41, a(868868) = 43
(End)


LINKS



MAPLE

f:= proc(n) local p;
p:= 7;
while min([n, n+1, n+2, n+3, n+4] mod p) = 0 do p:= nextprime(p) od:
p
end proc:


MATHEMATICA

Table[k=2; While[First[Union[CoprimeQ[k, #]&/@(n+Range[0, 4])]]== False, k++]; k, {n, 80}] (* Harvey P. Dale, Jul 07 2011 *)


PROG

(Haskell)
import Data.List (elemIndex)
import Data.Maybe (fromJust)
a053673 n = 2 + fromJust
(elemIndex 1 $ map (gcd $ foldl1 lcm $ take 5 [n..]) [2..])


CROSSREFS



KEYWORD

nonn,easy,nice


AUTHOR



EXTENSIONS

More terms from Andrew Gacek (andrew(AT)dgi.net), Feb 21 2000 and James A. Sellers, Feb 22 2000


STATUS

approved



