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A131460
Residues of 3^(2^(p(n)-1)+1) for Mersenne numbers with prime indices.
6
0, 5, 22, 118, 1803, 8182, 131062, 524278, 498820, 271127480, 2147483638, 44060320367, 967030303245, 7907414671310, 49672464783624, 5545884378065500, 125222315103997360, 2305843009213693942, 130613131595363896897
OFFSET
1,2
COMMENTS
Mp is prime iff 3^(2^(p(n)-1)+1) is congruent to (-9) Mod Mp. Thus M7 = 127 is prime because 3^65 Mod 127 = 118 (=127-9) while M11 = 2047 is composite because 3^1025 Mod 2047 <> 2038.
LINKS
FORMULA
a(n) = 3^(2^(p(n)-1)+1) Mod 2^p(n)-1
EXAMPLE
a(5) = 3^(2^(11-1)+1) Mod 2^11-1 = 3^1025 Mod 2047 = 1803
KEYWORD
nonn
AUTHOR
Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 13 2007, Jul 20 2007
STATUS
approved