OFFSET
1,2
COMMENTS
EXAMPLE
MATHEMATICA
npd = 1; Do[npd = npd*Prime[n]; tn = 0; tt = 1; cp = npd/tt + tt; ct = 0; While[IntegerQ[cp], If[(cp >= (tt*2)) && PrimeQ[cp], ct = ct + 1]; tn = tn + 1; tt = 1; k1 = tn; o = 1; While[k1 > 0, k2 = Mod[k1, 2]; If[k2 == 1, tt = tt*Prime[o]]; k1 = (k1 - k2)/2; o = o + 1]; cp = npd/tt + tt]; Print[ct], {n, 1, 22}]
Table[ps=Prime[Range[n]]; cnt=0; Do[b=IntegerDigits[i, 2, n]; p=Times@@(ps^b) + Times@@(ps^(1-b)); If[PrimeQ[p], cnt++], {i, 0, 2^(n-1)-1}]; cnt, {n, 22}]
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Lei Zhou, Feb 15 2005
EXTENSIONS
a(28)-a(31) from James G. Merickel, Aug 07 2015
STATUS
approved