OFFSET
1,1
EXAMPLE
a(2) = 47 as f(f(f(f(2)))) = 47. a(7) = 3 as f(7) = 15 but g(7) = 3.
a(4) = 0 as f(4) = 4*2+1 = 9 is composite and (4-1)/2 is non integer.
MAPLE
f:=n->2*n+1: g:=n->(n-1)/2: for n from 1 to 100 do mf:=f(n): mg:=g(n): if isprime(mf) then while isprime(f(mf)) do mf:=f(mf) od: printf("%d, ", mf) elif n mod 2= 1 and isprime(mg) then while mg mod 2=1 and isprime(g(mg)) do mg:=g(mg) od: printf("%d, ", mg) else printf("%d, ", 0) fi od: # C. Ronaldo
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Nov 18 2003
EXTENSIONS
More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 26 2004
STATUS
approved