|
%I #24 Oct 22 2017 01:34:55
%S 3,4,5,7,9,11,15,17,21,23,27,31,33,35,39,41,45,47,51,55,57,61,63,65,
%T 69,71,75,77,81,83,87,91,93,97,105,107,111,113,117,121,129,131,135,
%U 139,141,143,147,155,159,161,165
%N a(n+1) = 2a(n) - {largest prime < a(n)}.
%H Reinhard Zumkeller, <a href="/A033556/b033556.txt">Table of n, a(n) for n = 0..10000</a>
%F a(n+1) = 2*a(n) - A151799(a(n)). - _Reinhard Zumkeller_, Jul 26 2012
%t a[n_] := a[n] = 2*a[n-1] - NextPrime[ a[n-1], -1]; a[0] = 3; Table[ a[n], {n, 0, 50}] (* _Jean-François Alcover_, Sep 24 2012 *)
%t NestList[2#-NextPrime[#,-1]&,3,50] (* _Harvey P. Dale_, Jul 19 2014 *)
%o (Haskell)
%o a033556 n = a033556_list !! n
%o a033556_list = iterate (\x -> 2*x - fromInteger (a151799 x)) 3
%o -- _Reinhard Zumkeller_, Jul 26 2012
%o (PARI) a(n) = if(n==0,3,2*a(n-1)-precprime(a(n-1)-1)) \\ _Iain Fox_, Oct 18 2017
%o (PARI) first(n) = my(res = vector(n)); res[1] = 3; for(i = 2, n, res[i] = 2 * res[i - 1] - precprime(res[i - 1] - 1)); res \\ _David A. Corneth_, Oct 18 2017
%Y Cf. A007917, A151799.
%K nonn,easy,nice
%O 0,1
%A armand turpel (armand_t(AT)yahoo.com)
|
