OFFSET
1,1
COMMENTS
Composite numbers n such that Sum_{k=1..n-1} floor(k^3/n) = (1/4)*(n-2)*(n^2-1) (equality also holds for all primes). - Benoit Cloitre, Dec 08 2002
LINKS
Zak Seidov, Table of n, a(n) for n = 1..11999.
Eric Weisstein's World of Mathematics, Lehmer's Constant
Eric Weisstein's World of Mathematics, Prime Sums
MATHEMATICA
Complement[Select[Range[3, 281, 2], SquareFreeQ], Prime[Range[PrimePi[281]]]] (* Harvey P. Dale, Jan 26 2011 *)
PROG
(Haskell)
a024556 n = a024556_list !! (n-1)
a024556_list = filter ((== 0) . a010051) $ tail a056911_list
-- Reinhard Zumkeller, Apr 12 2012
(PARI) is(n)=n>1&&n%2&&!isprime(n)&&issquarefree(n) \\ Charles R Greathouse IV, Apr 12 2012
(PARI) forstep(n=3, 273, 2, k=omega(n); if(k>1&&bigomega(n)==k, print1(n, ", "))) \\ Hugo Pfoertner, Dec 19 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 22 2000
EXTENSIONS
More terms from James A. Sellers, May 22 2000
STATUS
approved