

A108184


a(n) = smallest prime such that a(n) + 2n is also prime and such that a(n) > a(n1).


4



2, 3, 7, 11, 23, 31, 41, 47, 67, 71, 83, 109, 113, 131, 139, 149, 167, 193, 197, 233, 241, 251, 263, 271, 283, 317, 331, 347, 353, 373, 379, 401, 439, 443, 479, 487, 491, 503, 523, 541, 563, 571, 577, 587, 613, 619, 641, 727, 733, 761, 787, 809, 863, 877
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OFFSET

0,1


COMMENTS

Increasing primes p such that p + 2n is prime.


LINKS



EXAMPLE

a(0)=2 since 2+0=2 is prime; a(1)=3 since 3+2=5 is prime.
a(2)=7 since 7+4=11 is prime; 5 is not in the sequence since 5+4=9 is not prime.


MAPLE

A108184 := proc(n) option remember; if n = 1 then 3; else for a from procname(n1)+1 do if isprime(a) and isprime(a+2*n) then RETURN(a) ; fi; od: fi; end: seq(A108184(n), n=1..100) ; # R. J. Mathar, Jan 31 2009


MATHEMATICA

t = {2}; Do[p = NextPrime[t[[1]]]; While[! PrimeQ[p + 2 n], p = NextPrime[p]]; AppendTo[t, p], {n, 100}]; t (* T. D. Noe, Feb 04 2014 *)


PROG

(PARI) A108184(maxp) = {my(a=[2], n=1); forprime(p=3, maxp, if(isprime(p+2*n), n++; a=concat(a, p))); a} \\ Colin Barker, Feb 03 2014


CROSSREFS



KEYWORD

easy,nonn


AUTHOR



EXTENSIONS



STATUS

approved



