A154274 Primes of the form: nonprime(prime(n)) - (-1)^n.

2, 3, 17, 19, 71, 97, 127, 131, 139, 191, 193, 227, 229, 251, 281, 337, 349, 353, 389, 443, 503, 541, 557, 563, 571, 613, 659, 701, 719, 727, 743, 877, 911, 971, 1031, 1087, 1091, 1103, 1217, 1297, 1301, 1409, 1439, 1451, 1481, 1531, 1549, 1657, 1697, 1741

Offset

1,1

Comments

Where n-th "prime nonprime" = A141468(A000040(n))) and 1st "prime nonprime" = 0.

Links

Table of n, a(n) for n=1..50.

Example

For n=1, nonprime(prime(1)) - (-1)^1 = nonprime(2)+1 = 1+1 = 2 (prime), so a(1)=2.
For n=2, nonprime(prime(2)) - (-1)^2 = nonprime(3)-1 = 4-1 = 3(prime), so a(2)=3.
For n=3, nonprime(prime(3)) - (-1)^3 = nonprime(5)+1 = 8+1 = 9 (composite).
For n=4, nonprime(prime(4)) - (-1)^4 = nonprime(7)-1 = 10-1 = 9 (composite).
For n=5, nonprime(prime(5)) - (-1)^5 = nonprime(11)+1 = 16+1 = 17 (prime), so a(3)=17, etc.

Maple

A141468 := proc(n) if n <= 2 then n-1 ; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od; fi: end: for n from 1 to 400 do p := A141468(ithprime(n))-(-1)^n ; if isprime(p) then printf("%d, ", p); fi; od: # R. J. Mathar, Aug 14 2009

Crossrefs

Cf. A000040, A141468.

Sequence in context: A215376 A051074 A051094 * A235628 A140834 A121409

Adjacent sequences: A154271 A154272 A154273 * A154275 A154276 A154277

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jan 06 2009

Extensions

Corrected and extended by R. J. Mathar, Aug 14 2009

Status

approved