OFFSET
2,1
REFERENCES
D. E. Knuth, The Art of Computer Programming Second Edition. Vol. 2, Seminumerical Algorithms. Chapter 4.5.4 Factoring into Primes, Table 1, Page 390, Addison-Wesley, Reading, MA, 1981.
LINKS
G. C. Greubel, Table of n, a(n) for n = 2..1000
FORMULA
a(n) = 2^n - precprime(precprime(2^n)-1)
EXAMPLE
a(2)=2 because precprime(4)=3, and precprime(2)=2.
MATHEMATICA
Table[2^n - NextPrime[2^n, -2], {n, 2, 64}] (* T. D. Noe, Jan 24 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Washington Bomfim, Jan 23 2012
STATUS
approved