OFFSET
1,2
LINKS
FORMULA
a(n) = Sum_{i=1..n} (2*n - i) * c(i), where c is the prime characteristic (A010051).
MATHEMATICA
Table[Sum[(2 n - i) (PrimePi[i] - PrimePi[i - 1]), {i, n}], {n, 80}]
Table[Total[Select[IntegerPartitions[2 n, {2}], PrimeQ[#[[2]]]&][[All, 1]]], {n, 60}] (* Harvey P. Dale, Apr 19 2020 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Oct 22 2017
STATUS
approved