A228357 Numbers n such that sum of all primes <=n is not prime.

1, 5, 6, 11, 12, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 41, 42, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

6 is in the sequence since 2+3+5=10 is not prime.

Mathematica

t = {}; s = 0; Do[If [PrimeQ[n], s+ = n]; If[!PrimeQ[s], AppendTo[t, n]], {n, 120}]; t
Position[Accumulate[Table[If[PrimeQ[n], n, 0], {n, 100}]], _?(!PrimeQ[ #]&)]// Flatten//Rest (* Harvey P. Dale, Jul 02 2018 *)

Prog

(Magma) [n: n in [1..120] | not IsPrime(s) where s is &+PrimesUpTo(n)];

Crossrefs

Cf. A034387, A228102.

Sequence in context: A139071 A092296 A046608 * A215033 A047264 A343405

Adjacent sequences: A228354 A228355 A228356 * A228358 A228359 A228360

Keyword

nonn,easy

Author

Vincenzo Librandi, Aug 21 2013

Status

approved