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A243591
Numbers n such that floor((3/2)^n)-floor((3/2)^(n-1)) is a prime number.
0
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
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
Sequence in context: A172180 A193959 A093667 * A189012 A030415 A120516
KEYWORD
nonn,more,hard
AUTHOR
Pierre CAMI, Jun 07 2014
STATUS
approved