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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 T. D. Noe, Table of n, a(n) for n = 0..10000 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 Cf. A020483, A237055 Sequence in context: A228592 A034795 A165318 * A049091 A039787 A267503 Adjacent sequences: A108181 A108182 A108183 * A108185 A108186 A108187 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.)