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A108184 a(n) = smallest prime such that a(n) + 2n is also prime and such that a(n) > a(n-1). 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 (list; graph; refs; listen; history; text; internal format)
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(n-1)+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
Sequence in context: A228592 A034795 A165318 * A049091 A039787 A267503
KEYWORD
easy,nonn
AUTHOR
Giovanni Teofilatto, Jun 28 2005
EXTENSIONS
Edited and extended by Ray Chandler, Jul 07 2005
Edited by N. J. A. Sloane, Feb 11 2009 at the suggestion of R. J. Mathar
STATUS
approved

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Last modified May 24 06:10 EDT 2024. Contains 372772 sequences. (Running on oeis4.)