OFFSET
2,1
COMMENTS
See A054892 for another version.
FORMULA
a(n) = {min (prime(k)): sum_{i=0..n-1} prime(k+i) = 0 mod n, k>1 }. - R. J. Mathar, Nov 27 2007
EXAMPLE
For n=2 we add prime(2)+prime(3)=3+5=8 which is already a multiple of n=2, so we add the first of the primes, 3, at a(n=2).
For n=5 we test 3+5+7+11+13=39 against being a multiple of n=5, then 5+7+11+13+17=53, then 7+11+13+17+19=67 etc. and find that 71+73+79+83+89=395 is a multiple. We place the smallest member in this sequence of 5 primes, 71, at a(n=5).
MAPLE
A132809 := proc(n) local i, j ; for i from 2 do if add( ithprime(i+j), j=0..n-1) mod n = 0 then RETURN(ithprime(i)) ; fi ; od: end: seq(A132809(n), n=2..80) ; # R. J. Mathar, Nov 27 2007
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Enoch Haga, Sep 01 2007
EXTENSIONS
Edited by R. J. Mathar, Nov 27 2007
STATUS
approved