A141557 Nonprimes of form (p(c(n))-c(p(n))), where c(n)=n-th composite and p(n)=n-th prime.

1, 9, 9, 9, 15, 16, 18, 25, 21, 27, 26, 21, 22, 21, 35, 38, 35, 34, 33, 39, 49, 49, 33, 52, 49, 39, 48, 48, 49, 48, 60, 49, 52, 58, 58, 63, 75, 65, 65, 75, 81, 84, 77, 65, 69, 72, 72, 69, 65, 65, 75, 68, 77, 86, 94, 85, 95, 90, 94, 88, 98, 102, 99, 96, 93, 94, 94, 100, 91, 87, 90

Offset

1,2

Links

Table of n, a(n) for n=1..71.

Example

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

Crossrefs

Cf. A000040, A002808.

Sequence in context: A293832 A277223 A144586 * A072563 A206011 A192984

Adjacent sequences: A141554 A141555 A141556 * A141558 A141559 A141560

Keyword

nonn

Author

Juri-Stepan Gerasimov, Aug 14 2008

Extensions

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

Status

approved