A144427 - OEIS

A144427

Primes of the form (prime(n) + (-1)^n*3)/2.

3, 5, 7, 11, 19, 23, 37, 41, 47, 53, 67, 67, 71, 73, 83, 97, 101, 113, 127, 127, 137, 137, 157, 181, 193, 193, 199, 223, 223, 229, 233, 241, 307, 311, 331, 337, 353, 373, 379, 397, 421, 433, 457, 467, 487, 487, 503, 547, 557, 563, 563, 577, 599, 607, 613, 613

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

The first five integers n at which (prime(n) + (-1)^n*3)/2 yields a prime are 2, 4, 7, 8 and 13, so

a(1) = (prime(2) + (-1)^2)/2 = (3 + 3)/2 = 3.

a(2) = (prime(4) + (-1)^4)/2 = (7 + 3)/2 = 5.

a(3) = (prime(7) + (-1)^7)/2 = (17 - 3)/2 = 7.

a(4) = (prime(8) + (-1)^8)/2 = (19 + 3)/2 = 11.

a(5) = (prime(13) + (-1)^13)/2 = (41 - 3)/2 = 19.

MAPLE

for n from 1 to 300 do p := ithprime(n) ; c := (p+3*(-1)^n)/2 ; if type(c, 'integer') then if isprime(c) then printf("%d, ", c) ; end if; end if; end do: # R. J. Mathar, May 01 2010

PROG

(PARI) for(n=2, 1e3, if(isprime(k=(prime(n)+(-1)^n*3)/2), print1(k", "))) \\ Altug Alkan, Oct 18 2015

CROSSREFS

Cf. A000040.

Sequence in context: A111052 A138536 A093929 * A082603 A362250 A161420

Adjacent sequences: A144424 A144425 A144426 * A144428 A144429 A144430

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Oct 01 2008

EXTENSIONS

Corrected (337 inserted, 367 removed) by R. J. Mathar, May 01 2010

STATUS

approved