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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). 3
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 April 22 07:15 EDT 2021. Contains 343162 sequences. (Running on oeis4.)