A073425 -id:A073425 - cp's OEIS frontend

A162310 The count of lesser-twin-primes smaller than the n-th isolated prime.

0, 4, 5, 6, 6, 7, 8, 8, 8, 8, 10, 10, 10, 12, 12, 12, 12, 15, 15, 16, 17, 17, 17, 18, 19, 19, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 25, 25, 25, 25, 26, 26, 26, 27, 27, 28, 29, 29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30

Offset: 1

Juri-Stepan Gerasimov, Jul 01 2009

nonn

The count of members of A001359 smaller than A007510(n).

			a(1)=0 because there is no twin prime smaller than 2.
a(2)= 4 counts the numbers 3, 5, 11, and 17 all smaller than 23.
a(3) = 5 counts the numbers 3, 5, 11, 17, and 29 all smaller than 37.

Cf. A000040, A141468, A073425.

Entried checked by R. J. Mathar, Sep 23 2009

A163249 Sum of prime(n) and number of numbers from this set less than n-th nonprime number (A018252(n)).

Original entry on oeis.org

2, 5, 8, 11, 15, 17, 22, 25, 29, 35, 38, 45, 49, 51, 56, 62, 68, 70, 76, 81, 84, 90, 94, 100, 108, 113, 115, 119, 122, 127, 141, 145, 152, 154, 164, 166, 172, 179, 183, 189, 195, 197, 208, 211, 215, 217, 229, 241, 246, 248

Offset: 1

Jaroslav Krizek, Jul 23 2009

a(n) = Sum of n-th nonprime number (A018252(n)) and number of numbers from this set less than n-th prime (A000040(n)).

a(n) = prime(n) + A073425(n-1) = A018252(n) + A014689(n) = prime(n) + A018252(n)- n = prime(n) + A002808(n) - n.

cp's OEIS Frontend

A162310 The count of lesser-twin-primes smaller than the n-th isolated prime.

Views

Author

Keywords

Comments

Examples

Crossrefs

Extensions

A163249 Sum of prime(n) and number of numbers from this set less than n-th nonprime number (A018252(n)).

Views

Author

Keywords

Comments

Formula