OFFSET
1,1
COMMENTS
Squarefree numbers of the form p*q*r, where p < q < r = primes with q = 2*p + 1 and r = 2*q + 1; that is, r = 4*p + 3.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
5719229 = 89*179*359, 179 = 2*89 + 1, 359 = 2*179 + 1.
MATHEMATICA
sfQ[n_]:=Module[{q=2n+1, r}, r=2q+1; AllTrue[{q, r}, PrimeQ]&& SquareFreeQ[ n*q*r]]; 3#+10#^2+8#^3&/@Select[Prime[Range[400]], sfQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 26 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Nov 16 2013
STATUS
approved