OFFSET
1,5
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
FORMULA
G.f.: Product_{k>=1} 1/(1 - x^A005384(k)). - Andrew Howroyd, Dec 28 2017
EXAMPLE
e(10) = #{5+5,5+3+2,3+3+2+2,2+2+2+2+2} = 4;
e(11) = #{11,5+3+3,5+2+2+2,3+3+3+2,3+2+2+2+2} = 5.
MATHEMATICA
terms = 1000;
sgprimes = Select[Prime[Range[terms]], PrimeQ[2# + 1]&];
CoefficientList[Times @@ (1/(1 - x^sgprimes) + O[x]^(terms+1)), x] // Rest (* Jean-François Alcover, Dec 17 2021 *)
PROG
(PARI)
ok(n)={isprime(n) && isprime(2*n+1)}
{my(n=80); Vec(prod(k=1, n, if(ok(k), 1/(1-x^k) + O(x*x^n), 1))-1, -n)} \\ Andrew Howroyd, Dec 28 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Aug 09 2009
STATUS
approved