The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A098170 Smallest prime p such that prime(n)#/2 + 2*p is prime where p > 3, except p=2 for n=1. 2
 2, 5, 7, 11, 13, 19, 29, 31, 29, 31, 41, 41, 43, 83, 59, 83, 163, 97, 193, 89, 89, 173, 113, 107, 131, 157, 131, 109, 113, 467, 151, 239, 167, 263, 233, 211, 251, 167, 599, 199, 199, 211, 313, 241, 509, 887, 307, 227, 419, 479, 317, 269, 653, 281, 307, 277, 499 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..200 EXAMPLE For n=4, A002110(4)/2=210/2=105. 105+2*5 is not prime. 105+2*7 is not prime. 105+2*11 is prime, so a(4)=11. MAPLE A098170 := proc(n)     local pri, j, jmin;     pri := A002110(n)/2 ;     if n = 1 then         jmin := 1;     else         jmin := 3;     end if;     for j from jmin do         if isprime(pri+2*ithprime(j)) then             return ithprime(j) ;         end if;     end do: end proc: # R. J. Mathar, Apr 12 2017 MATHEMATICA Primorial[n_Integer] := Block[{k = Product[ Prime[ j], {j, n}]}, k]; f[n_] := Block[{p = Primorial[n]/2}, If[n == 1, j = 1, j = 2]; While[ !PrimeQ[p + 2Prime[j]], j++ ]; Prime[j]]; Table[ f[n], {n, 57}] (* Robert G. Wilson v, Sep 04 2004 *) CROSSREFS The indices of the p are in A098171. Sequence in context: A074833 A293859 A045347 * A256396 A291280 A120330 Adjacent sequences:  A098167 A098168 A098169 * A098171 A098172 A098173 KEYWORD nonn AUTHOR Pierre CAMI, Aug 30 2004 EXTENSIONS Edited and extended by Robert G. Wilson v, Sep 04 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 2 17:49 EDT 2021. Contains 346428 sequences. (Running on oeis4.)