OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..750 from Harvey P. Dale)
FORMULA
EXAMPLE
4*45-1 = 179, 8*45-1 = 359, 16*45-1 = 719, 32*45-1 = 1439 and 64*45-1 = 2879 are primes, so 359 is a term.
MATHEMATICA
8#-1&/@Select[Range[720000], AllTrue[{4, 8, 16, 32, 64}#-1, PrimeQ]&] (* Harvey P. Dale, Jan 17 2023 *)
Select[Table[2^Range[2, 6] n-1, {n, 750000}], AllTrue[#, PrimeQ]&][[;; , 2]] (* Harvey P. Dale, Jun 03 2023 *)
PROG
(PARI) is(k) = if(k % 8 == 7, my(m = k\8 + 1); isprime(4*m-1) && isprime(8*m-1) && isprime(16*m-1) && isprime(32*m-1) && isprime(64*m-1), 0); \\ Amiram Eldar, May 13 2024
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 23 2004
EXTENSIONS
Corrected by T. D. Noe, Nov 15 2006
STATUS
approved