A164121 a(1)=1. a(n) = the smallest odd integer > a(n-1) such that a(n)*2 - a(n-1) is prime.

1, 3, 5, 9, 11, 15, 17, 23, 27, 29, 33, 35, 39, 41, 47, 53, 57, 59, 63, 65, 69, 71, 75, 77, 83, 93, 95, 99, 101, 105, 107, 117, 127, 129, 133, 135, 137, 143, 147, 149, 153, 155, 159, 161, 167, 173, 177, 179, 185, 189, 191, 195, 197, 213, 221, 225, 227, 233, 237, 239

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

R:= 1; x:= 1: count:= 1:
for y from x+2 by 2 do
  if isprime(2*y-x) then
    R:= R, y; x:= y; count:= count+1;
    if count = 100 then break fi;
  fi
od:
R; # Robert Israel, Mar 22 2023

Mathematica

soi[a_]:=Module[{k=a+2}, While[!PrimeQ[2k-a], k=k+2]; k]; NestList[soi, 1, 60] (* Harvey P. Dale, Sep 02 2023 *)

Crossrefs

Cf. A164122.

Sequence in context: A040976 A268174 A166104 * A333171 A078651 A268732

Adjacent sequences: A164118 A164119 A164120 * A164122 A164123 A164124

Keyword

nonn

Author

Leroy Quet, Aug 10 2009

Extensions

More terms from R. J. Mathar, Oct 24 2009

Status

approved