|
Search: id:A090808
|
|
|
| A090808 |
|
Numbers n such that numerator(sum(i=1,n, prime(i)/prime(i+1))) is prime. |
|
+0
1
|
| |
|
|
OFFSET
|
1,2
|
|
|
EXAMPLE
|
a(2)=2 2/3 + 3/5 = 19/15 and 19 is prime and prime(2+1)=5.
a(3)=4 because 2/3+3/5+5/7+7/11 = 3023/1155 and 3023 is prime and prime(4+1)=11.
|
|
PROGRAM
|
(PARI) pp(n)= s=0; for (i=1, n, s=s+prime(i)/prime(i+1)); return(s); for (i=1, 800, if(isprime(numerator(pp(i))), print(i)))
|
|
CROSSREFS
|
Sequence in context: A071865 A127596 A111871 this_sequence A074716 A090889 A096012
Adjacent sequences: A090805 A090806 A090807 this_sequence A090809 A090810 A090811
|
|
KEYWORD
|
hard,nonn
|
|
AUTHOR
|
mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 16 2004
|
|
|
Search completed in 0.002 seconds
|
