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A135630
2^(prime(n) - 2) - 1.
1
0, 1, 7, 31, 511, 2047, 32767, 131071, 2097151, 134217727, 536870911, 34359738367, 549755813887, 2199023255551, 35184372088831, 2251799813685247, 144115188075855871, 576460752303423487, 36893488147419103231, 590295810358705651711
OFFSET
1,3
LINKS
FORMULA
a(n) = 2^(A000040(n)-2) - 1 = 2^(A040976(n)) - 1 = (2^A000040(n)/4) - 1 = (A061286(n)/2) - 1.
EXAMPLE
a(4)=31 because the 4th prime number is 7 and 7-2=5 and 2^5=32 and 32-1=31.
MATHEMATICA
Table[2^(Prime[n]-2)-1, {n, 20}] (* Harvey P. Dale, Feb 25 2011 *)
PROG
(Magma) [2^(NthPrime(n)-2)-1: n in [1..30]]; // Vincenzo Librandi, Sep 06 2014
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Mar 01 2008
EXTENSIONS
More terms from Harvey P. Dale, Feb 25 2011
STATUS
approved