A141639 Primes of the form c(c(i)-3)-3, where A002808(i)=c(i)=i-th composite.

5, 7, 11, 13, 17, 19, 31, 37, 41, 43, 53, 59, 61, 71, 73, 79, 83, 89, 97, 103, 109, 113, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 251, 257, 263, 269, 271, 281, 293, 307, 313, 317, 337, 347, 349, 353, 359

Offset

1,1

Links

Table of n, a(n) for n=1..57.

Example

If i=1, then
c(c(1)-3)-3=c(4-3)-3=4-3=1 (nonprime).
If i=2, then
c(c(2)-3)-3=c(6-3)-3=c(3)-3=8-3=5=a(1).
If i=3, then
c(c(3)-3)-3=c(8-3)-3=c(5)-3=10-3=7=a(2).
If i=4, then
c(c(4)-3)-3=c(9-3)-3=c(6)-3=12-3=9 (nonprime).
If i=5, then
c(c(5)-3)-3=c(10-3)-3=c(7)-3=14-3=11=a(3),
etc.

Mathematica

Module[{nn=500, cmps}, cmps=Select[Range[nn], CompositeQ]; Select[ Table[ cmps[[cmps[[n]]-3]]-3, {n, 250}], PrimeQ]] (* Harvey P. Dale, Jun 17 2021 *)

Crossrefs

Cf. A002808, A000040.

Sequence in context: A253969 A191056 A314296 * A232558 A290246 A024891

Adjacent sequences: A141636 A141637 A141638 * A141640 A141641 A141642

Keyword

nonn

Author

Juri-Stepan Gerasimov, Sep 03 2008

Extensions

43, 59, 73, 227, 229, 347, 367 inserted by R. J. Mathar, Sep 05 2008

Status

approved