A191558 a(n) = 0 if n prime, otherwise n.

1, 0, 0, 4, 0, 6, 0, 8, 9, 10, 0, 12, 0, 14, 15, 16, 0, 18, 0, 20, 21, 22, 0, 24, 25, 26, 27, 28, 0, 30, 0, 32, 33, 34, 35, 36, 0, 38, 39, 40, 0, 42, 0, 44, 45, 46, 0, 48, 49, 50, 51, 52, 0, 54, 55, 56, 57, 58, 0, 60, 0, 62, 63, 64, 65, 66, 0, 68, 69, 70, 0, 72, 0, 74, 75, 76, 77, 78, 0, 80, 81, 82, 0, 84, 85, 86, 87, 88, 0, 90, 91, 92, 93, 94

Offset

1,4

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Formula

a(n) = n * A005171(n) = n - A061397(n). - R. J. Mathar, Jun 11 2011

Maple

A191558 := proc(n) if isprime(n) then 0; else n; end if; end proc:
seq(A191558(n), n=1..80) ; # R. J. Mathar, Jun 11 2011

Mathematica

Table[If[PrimeQ[n], 0, n], {n, 150}] (* Vincenzo Librandi, May 17 2014 *)
(*recurrence*)
Clear[t];
nn = 94;
t[1, 1] = 1;
t[n_, k_] :=
  t[n, k] =
   If[n == k, n*(1 - Product[t[n, k - i], {i, 1, k - 1}]),
    If[n > k, t[n - k, k], 1]];
Table[t[n, n], {n, 1, nn}](* Mats Granvik, Jul 05 2014 *)
Table[n (1 - PrimePi[n] + PrimePi[n - 1]), {n, 50}] (* Wesley Ivan Hurt, Jul 06 2014 *)

Prog

(Magma) [IsPrime(n) select 0 else n: n in [1..100]]; // Vincenzo Librandi, May 17 2014

Crossrefs

Cf. A002808.

Sequence in context: A327964 A085562 A037282 * A075083 A179939 A163407

Adjacent sequences: A191555 A191556 A191557 * A191559 A191560 A191561

Keyword

nonn,easy

Author

Vincenzo Librandi, Jun 07 2011

Status

approved