A245601 Smallest prime Q such that prime(n)*(2*Q)^prime(n)+1 is prime.

3, 2, 7, 2, 181, 503, 43, 281, 919, 397, 2099, 389, 163, 89, 5641, 751, 1951, 353, 2, 3709, 4673, 1607, 769, 7699, 107, 7069, 17, 13147, 7841, 97, 5741, 2383, 5557, 251, 9661, 14969, 269, 2753, 18451, 2797, 4729, 29, 15649, 5387, 8539, 13001, 1481, 2

Offset

1,1

Links

Pierre CAMI and Jens Kruse Andersen, Table of n, a(n) for n = 1..200 (first 100 terms from Pierre CAMI)

Example

2*(2*2)^2 + 1 = 33 composite.
2*(2*3)^2 + 1 = 73 prime so a(1) = 3.

Mathematica

a245601[n_Integer] := Catch[
  Do[
   If[And[PrimeQ[Q], PrimeQ[Prime[n]*(2*Q)^Prime[n] + 1]] == True,
    Throw[Q]],
   {Q, 1000000}]
  ]; Map[a245601, Range[50]] (* Michael De Vlieger, Aug 03 2014 *)

Prog

(PFGW & SCRIPT)
SCRIPT
DIM i, 0
DIM n
DIMS t
OPENFILEOUT myf, b(n).txt
LABEL loop1
SET i, i+1
IF i>100 THEN END
SET n, 0
LABEL loop2
SET n, n+1
SETS t, %d, %d\,; p(i); p(n)
PRP p(i)*(2*p(n))^p(i)+1, t
IF ISPRP THEN GOTO a
GOTO loop2
LABEL a
WRITE myf, t
GOTO loop1
(PARI) a(n)=for(k=1, 10^5, if(ispseudoprime(prime(n)*(2*prime(k))^prime(n)+1), return(prime(k))))
n=1; while(n<100, print1(a(n), ", "); n++) \\ Derek Orr, Jul 27 2014

Crossrefs

Cf. A245597, A245598, A245600.

Sequence in context: A349211 A266664 A308439 * A355934 A296513 A099378

Adjacent sequences: A245598 A245599 A245600 * A245602 A245603 A245604

Keyword

nonn

Author

Pierre CAMI, Jul 27 2014

Status

approved