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A139291
a(n) = 2^(2*prime(n) - 3) - 1.
6
1, 7, 127, 2047, 524287, 8388607, 2147483647, 34359738367, 8796093022207, 36028797018963967, 576460752303423487, 2361183241434822606847, 604462909807314587353087, 9671406556917033397649407, 2475880078570760549798248447, 10141204801825835211973625643007
OFFSET
1,2
FORMULA
a(n) = A139286(n)/4 - 1.
a(n) = A000225(A131426(n)). - Max Alekseyev, Mar 07 2020
a(n) = A139290(n) - 1. - Omar E. Pol, Mar 10 2020
MATHEMATICA
(2^(2#-1))/4-1&/@Prime[Range[20]] (* Harvey P. Dale, May 08 2011 *)
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 13 2008
EXTENSIONS
Edited by Max Alekseyev, May 03 2009, Mar 07 2020
STATUS
approved