OFFSET
1,1
EXAMPLE
A103379(21) = 4 = 2 * 2, which is semiprime, hence 4 is in this sequence.
MAPLE
isA103379 := proc(n)
option remember ;
local i ;
for i from 1 do
if A103379(i) = n then
return true ;
elif A103379(i) > n then
return false ;
fi;
od:
end proc:
A103399 := proc(n)
option remember ;
local a, i ;
if n = 1 then
4;
else
for a from procname(n-1)+1 do
if numtheory[bigomega](a) = 2 then
if isA103379(a) then
return a ;
fi;
fi;
end do:
end if;
end proc:
for n from 1 do
printf("%d, \n", A103399(n)) ;
end do: # R. J. Mathar, Aug 30 2008
MATHEMATICA
SemiprimeQ[n_]:=Plus@@FactorInteger[n][[All, 2]]?2; Clear[a]; k11; Do[a[n]=1, {n, k+1}]; a[n_]:=a[n]=a[n-k]+a[n-k-1]; A103379=Array[a, 100] A103389=Union[Select[Array[a, 1000], PrimeQ]] A103399=Union[Select[Array[a, 300], SemiprimeQ]] N[Solve[x^12 - x - 1 == 0, x], 111][[2]] (* Program, edit and extension by Ray Chandler and Robert G. Wilson v *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Feb 15 2005
EXTENSIONS
Corrected from a(15) on by R. J. Mathar, Aug 30 2008
STATUS
approved