A141558 Primes of form (p(c(n))-c(p(n))), where c(n)=n-th composite and p(n)=n-th prime.

5, 17, 17, 19, 31, 31, 31, 37, 47, 43, 47, 47, 41, 59, 59, 71, 67, 71, 79, 67, 61, 89, 97, 89, 103, 103, 107, 101, 101, 107, 107, 127, 127, 131, 131, 149, 151, 137, 127, 163, 173, 173, 167, 179, 167, 163, 157, 163, 167, 149, 173, 167, 181, 193, 179, 179, 223, 223

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Example

If n=1, c(1)=4, p(1)=2, then p(4)-c(2)=7-6=1 (nonprime).
If n=2, c(2)=6, p(2)=3, then p(6)-c(3)=13-8=5=a(1).
If n=3, c(3)=8, p(3)=5, then p(8)-c(5)=19-10=9 (composite).
If n=4, c(4)=9, p(4)=7, then p(9)-c(7)=23-14=9 (composite).
If n=5, c(5)=10, p(5)=11, then p(10)-c(11)=29-20=9 (composite).
If n=6, c(6)=12, p(6)=13, then p(12)-c(13)=37-22=15 (composite).
If n=7, c(7)=14, p(7)=17, then p(14)-c(17)=43-27=16 (composite).
If n=8, c(8)=15, p(8)=19, then p(15)-c(19)=47-30=17=a(2).
If n=9, c(9)=16, p(9)=23, then p(16)-c(23)=53-35=18 (composite).
If n=10, c(10)=18, p(10)=29, then=p(18)-c(29)=61-44=17=a(3).
If n=11, c(11)=20, p(11)=31, then p(20)-c(31)=71-46=25 (composite).
If n=12, c(12)=21, p(12)=37, then p(21)-c(37)=73-54=19=a(4).
If n=13, c(13)=22, p(13)=41, then p(22)-c(41)=79-58=21 (composite).
If n=14, c(14)=24, p(14)=43, then p(24)-c(43)=89-62=27 (composite).
If n=15, c(15)=25, p(15)=47, then p(25)-c(47)=97-66=31=a(5).
If n=16, c(16)=26, p(16)=53, then p(26)-c(53)=101-75=26 (composite), etc.

Crossrefs

Cf. A000040, A002808.

Sequence in context: A304851 A237437 A128895 * A304217 A305248 A231710

Adjacent sequences: A141555 A141556 A141557 * A141559 A141560 A141561

Keyword

nonn

Author

Juri-Stepan Gerasimov, Aug 14 2008

Extensions

Edited, corrected and extended by Ray Chandler, Aug 19 2008

Status

approved