OFFSET
0,3
COMMENTS
Prime values of a(n) begin 3, 7, 23, 151, i.e., for n = 2, 3, 4, 5. Semiprime values of a(n) begin 4247 = 31 * 137, 1052823 = 3 * 350941, i.e., for n = 6, 7. - Jonathan Vos Post, May 09 2005
FORMULA
a(0) = 0, a(n) = a(n-1)+(2^(Fib(n+1)-1)).
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 30 1999
STATUS
approved