OFFSET
2,1
LINKS
Carlos Rivera, Problems & Puzzles.
EXAMPLE
a(7)=120 because 2*120-1, 3*120-1, 4*120-1, 5*120-1, 6*120-1 & 7*120-1 are prime and 120 is the smallest such number.
MATHEMATICA
a[n_] := Block[{k=2}, While[! AllTrue[k Range[2, n] - 1, PrimeQ], k += 2]; k]; a /@
Range[2, 8] (* Giovanni Resta, Mar 29 2017 *)
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Carlos Rivera, Jan 01 2007
EXTENSIONS
a(8) from Luke Pebody (luke.pebody(AT)gmail.com)
a(9)-a(10) from Vladimir Trushkov (vladimir(AT)trushkov.botik.ru)
a(11) from Farideh Firoozbakht
a(5) corrected by and a(12)-a(14) from Giovanni Resta, Mar 29 2017
STATUS
approved