OFFSET
1,1
COMMENTS
a(n) is the number whose binary representation is p 1's together with p-1 0's, where p is prime(n), for example: prime(3) = 5 so a(3) = 496 = 111110000 (2). - Omar E. Pol, Dec 12 2012
REFERENCES
C. Stanley Ogilvy and John T. Anderson, "Excursions in Number Theory", Oxford University Press, NY, 1966 pp. 20-23.
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..100
FORMULA
For n > 1, a(2n) = 9*T(k) + 1 ; a(2n+1) = 9*T(K) + 1, where T(n) = A000217(n), k = (A121290(n) - 1)/2, K = 2*A121290(n). - Lekraj Beedassy, Sep 12 2006
EXAMPLE
a(4) = 2^6(2^7 - 1) = 8128.
MATHEMATICA
Table[2^(Prime[n] - 1)(2^Prime[n] - 1), {n, 16}] (* Alonso del Arte, Dec 12 2012 *)
PROG
(PARI) { n=0; forprime (p=1, 542, write("b060286.txt", n++, " ", 2^(p - 1)*(2^p - 1)); ) } \\ Harry J. Smith, Jul 03 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Mar 23 2001
STATUS
approved