|
|
A089228
|
|
Numbers m such that 1 + Sum_{k=1..m} prime(k) is prime.
|
|
4
|
|
|
1, 3, 5, 7, 9, 13, 19, 25, 29, 31, 49, 51, 57, 97, 99, 103, 109, 119, 123, 127, 163, 169, 179, 185, 195, 207, 209, 211, 213, 217, 221, 223, 233, 235, 239, 251, 261, 269, 273, 289, 295, 297, 303, 325, 329, 333, 347, 369, 371, 375, 409, 439, 449, 453, 455, 467
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
EXAMPLE
|
25 is a term: 1 + Sum_{k=1..25} prime(k) = 1061 is prime.
|
|
MAPLE
|
a:=proc(n) if isprime(1+add(ithprime(k), k=1..n))=true then n else fi end: seq(a(n), n=1..600); # Emeric Deutsch, Jul 02 2005
# alternative
Primes:= select(isprime, [2, seq(2*i+1, i=1..10^5)]):
PS:= ListTools:-PartialSums(Primes):
select(t -> isprime(PS[t]+1), [$1..nops(PS)]); # Robert Israel, May 19 2015
|
|
MATHEMATICA
|
Position[1 + Accumulate@ Prime@ Range@ 600, _?(PrimeQ@# &)] // Flatten (* after Harvey P. Dale from A013916 *) (* Robert G. Wilson v, May 19 2015 *)
|
|
PROG
|
(PARI) for(n=1, 10^3, if(isprime(1+sum(i=1, n, prime(i))), print1(n, ", "))) \\ Derek Orr, May 19 2015
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|