A378020 a(n) = pi(A020482(n)) - pi(A020481(n)).

0, 0, 1, 2, 1, 3, 4, 3, 5, 6, 5, 7, 6, 5, 8, 9, 8, 7, 10, 9, 11, 12, 11, 13, 12, 11, 14, 13, 12, 15, 16, 15, 14, 17, 16, 18, 19, 18, 17, 20, 19, 21, 20, 19, 22, 21, 20, 14, 23, 22, 24, 25, 24, 26, 27, 26, 28, 27, 26, 23, 25, 24, 21, 29, 28, 30, 29, 28, 31, 32, 31, 30, 28, 29, 33, 34

Offset

1,4

Links

Table of n, a(n) for n=1..76.

Formula

a(n) = A377972(n) - A377758(n).

Mathematica

Table[Module[{p = 2, q},
  While[True, q = 2 n - p; If[PrimeQ[p] && PrimeQ[q], Break[]];
   p = NextPrime[p]]; PrimePi[q] - PrimePi[p]], {n, 2, 100}]

Crossrefs

Cf. A000720, A020481, A020482, A377758, A377972.

Sequence in context: A324749 A022466 A144254 * A133310 A362563 A077608

Adjacent sequences: A378017 A378018 A378019 * A378021 A378022 A378023

Keyword

nonn

Author

Michel Eduardo Beleza Yamagishi, Nov 14 2024

Status

approved