A101787 a(n) = |S(n)| where S(n) = {i : 1 <= i <= n and 4*i-1 and 8*i-1 are primes}.

1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10

Offset

1,3

Comments

Number of Lucasian primes that do not exceed 4*n-1. [Corrected by Amiram Eldar, May 23 2024]

Links

Table of n, a(n) for n=1..94.

Mathematica

Accumulate[Table[Boole[And @@ PrimeQ[{4, 8}*i - 1]], {i, 1, 100}]] (* Amiram Eldar, May 23 2024 *)

Crossrefs

Cf. A002515, A101788.

Sequence in context: A156752 A345073 A086673 * A343607 A269024 A244160

Adjacent sequences: A101784 A101785 A101786 * A101788 A101789 A101790

Keyword

easy,nonn

Author

Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004

Extensions

Name corrected by Amiram Eldar, May 23 2024

Status

approved