OFFSET
1,5
FORMULA
a(n) = A061357(2^(n-1) - 1) for n > 2. - Charles R Greathouse IV, Mar 08 2013
EXAMPLE
a(4) = 1 because 2^4 = 16 = 2 + 3 + 11 (1 partition),
a(5) = 3 because 2^5 = 32 = 2 + 7 + 23 = 2 + 11 + 19 = 2 + 13 + 17 (3 partitions).
MATHEMATICA
Do[Print[{k, n=2^k; s=0; Do[p=Prime[i]; Do[q=Prime[j]; r=n-p-q; If[r>q && PrimeQ[r], s++], {j, i+1, PrimePi[(n-p)/2]}], {i, 1}]; s}], {k, 30}]
Table[m = 2^n - 2; cnt = 0; p = 3; While[p < m/2, If[PrimeQ[m - p], cnt++]; p = NextPrime[p]]; cnt, {n, 20}] (* T. D. Noe, Mar 08 2013 *)
PROG
(PARI) a(n)=my(N=2^n-2, s); forprime(p=3, N/2-1, s+=ispseudoprime(N-p)); s \\ Charles R Greathouse IV, Mar 08 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Mar 08 2013
STATUS
approved