A161811 Difference between nonprime(n+2) and nonprime(n).

4, 5, 4, 3, 2, 3, 4, 3, 2, 3, 4, 3, 2, 3, 3, 2, 2, 2, 3, 4, 3, 2, 2, 2, 3, 3, 2, 3, 4, 3, 2, 3, 3, 2, 2, 2, 3, 3, 2, 2, 2, 3, 4, 3, 2, 2, 2, 3, 3, 2, 3, 4, 3, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 3, 3, 2, 2, 2, 2, 2, 3, 3, 2, 3, 4, 3, 2, 3, 4, 3, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 3, 4

Offset

1,1

Comments

"nonprime(n)" is used for "n-th nonprime". Here the nonprimes start at 0 (see A141468), so nonprime(1) to nonprime(15) are 0, 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22.

Links

Table of n, a(n) for n=1..105.

Formula

a(n) = A141468(n+2)-A141468(n).

Example

nonprime(1+2)-nonprime(1) = 4-0; so a(1) = 4.
nonprime(5+2)-nonprime(5) = 10-8; so a(5) = 2.
nonprime(11+2)-nonprime(11) = 20-16; so a(11) = 4.

Mathematica

#[[3]]-#[[1]]&/@Partition[Select[Range[0, 150], !PrimeQ[#]&], 3, 1] (* Harvey P. Dale, Jul 08 2022 *)

Crossrefs

Cf. A031131, A141468.

Sequence in context: A366610 A175622 A071413 * A016717 A366153 A031349

Adjacent sequences: A161808 A161809 A161810 * A161812 A161813 A161814

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jun 20 2009

Extensions

Edited, corrected (a(11)=2 replaced by 4) and extended by Klaus Brockhaus, Jun 24 2009

Status

approved