OFFSET
1,4
FORMULA
a(n) = 2n * Sum_{i=1..floor((n-1)/2)} A010051(n-2i).
MATHEMATICA
Table[2 n*Sum[(PrimePi[n - 2 i] - PrimePi[n - 2 i - 1]), {i, Floor[(n - 1)/2]}], {n, 80}]
PROG
(PARI) a(n) = 2*n*sum(i=1, (n-1)\2, isprime(n-2*i)); \\ Michel Marcus, Apr 21 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 19 2018
STATUS
approved