OFFSET
1,1
COMMENTS
For n>1 largest prime factor of the denominator of A027611(2^n) = 2^n*(2^n)-th harmonic number. - Alexander Adamchuk, Aug 02 2006
REFERENCES
D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 2, p. 390.
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
Fred Curtis, C++ program for A014234
Harry J. Smith, PrimePi2 - Computes the Prime Pi(x) counting function [Broken link]
Harry J. Smith, PrimePi2 - Computes the Prime Pi(x) counting function [Cached copy]
MAPLE
a:= n-> prevprime(2^n+1):
seq(a(n), n=1..40); # Alois P. Heinz, Apr 23 2020
MATHEMATICA
PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; Table[ Abs[ PrevPrim[2^n]], {n, 1, 30} ]
Join[{2}, NextPrime[2^Range[2, 40], -1]] (* Harvey P. Dale, Jun 26 2011 *)
PROG
(C++) // see link above
(PARI) a(n) = precprime(2^n) \\ Michel Marcus, Aug 08 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Terms for n=31, n=32 added by Fred Curtis (fred(AT)f2.org), Dec 08 2009
STATUS
approved