A143738 Number of twin primes between n and n^2. Only smaller of twins (terms of A001359) are counted.

0, 1, 2, 2, 3, 3, 4, 5, 6, 6, 8, 8, 9, 11, 12, 14, 16, 16, 17, 17, 19, 20, 21, 22, 24, 26, 26, 26, 29, 30, 30, 31, 34, 36, 36, 39, 41, 42, 45, 45, 48, 49, 50, 53, 55, 59, 61, 63, 66, 66, 68, 70, 74, 74, 76, 77, 78, 83, 87, 90, 91, 93, 96, 100

Offset

1,3

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

For n = 6, between 6 and 36 the smaller of twin pairs are {11, 17, 29}, so a(6) = 3.

Mathematica

Table[Count[Table[PrimeQ[j] && PrimeQ[j + 2], {j, n, n*n}], True], {n, 1, 100}]

Prog

(Magma) [#[p:p in PrimesInInterval(n, n^2)|IsPrime(p+2)]:n in [1..80]]; // Marius A. Burtea, Dec 20 2019

Crossrefs

Cf. A001359, A080356.

Sequence in context: A113865 A358636 A347609 * A337766 A029071 A117144

Adjacent sequences: A143735 A143736 A143737 * A143739 A143740 A143741

Keyword

nonn

Author

Alen Skugor (askugor(AT)gmail.com), Aug 30 2008

Status

approved