A243591 Numbers n such that floor((3/2)^n)-floor((3/2)^(n-1)) is a prime number.

4, 5, 9, 10, 11, 12, 14, 19, 20, 32, 47, 89, 96, 105, 123, 143, 291, 354, 371, 424, 493, 526, 784, 906, 2670, 3506, 7096, 7938, 15046, 23959, 24920, 51182

Offset

1,1

Comments

a(33) > 4 * 10^5. - Lucas A. Brown, Nov 26 2020

Links

Table of n, a(n) for n=1..32.

Mathematica

Flatten[Position[Partition[Floor[(3/2)^Range[51200]], 2, 1], _?(PrimeQ[ #[[2]] -  #[[1]]]&), 1, Heads->False]]+1 (* Harvey P. Dale, May 17 2021 *)

Prog

(PFGW & SCRIPT)
SCRIPT
DIM k, 1
DIM q
OPENFILEOUT myf, a(n).txt
LABEL loop1
SET k, k+1
SET q, 3^k/2^k-3^(k-1)/2^(k-1)
PRP q
IF ISPRP THEN GOTO a
GOTO loop1
LABEL a
WRITE myf, k
GOTO loop1

Crossrefs

Cf. A242734, A242738.

Sequence in context: A172180 A193959 A093667 * A189012 A030415 A120516

Adjacent sequences: A243588 A243589 A243590 * A243592 A243593 A243594

Keyword

nonn,more,hard

Author

Pierre CAMI, Jun 07 2014

Status

approved