|
Search: id:A090660
|
|
|
| A090660 |
|
Numbers n such that n*nextprime((n-1)!)-nextprime(n!) < 0. |
|
+0
4
|
|
| 3, 4, 12, 28, 38, 42, 74, 78, 117, 155, 321, 341, 400, 428, 873, 1478, 6381, 26952
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
3*nextprime((3-1)!)-nextprime(3!) = 3*nextprime(2!)-nextprime(3!) = 3*2-7 = -1.
For n>2 n!+1 is prime <==> nextprime((n+1)!)>(n+1)nextprime(n!) and we can conjecture that for n>2 if n!+1 is prime then (n+1)!+1 is not prime.
|
|
MATHEMATICA
|
NextPrim[ n_ ] := Block[ {k = n + 1}, While[ !PrimeQ[ k ], k++ ]; k ]; Select[ Range[ 260 ], #*NextPrim[ (# - 1)! ] - NextPrim[ #! ] < 0 & ] (from Robert G. Wilson v)
|
|
CROSSREFS
|
Cf. A090661, A089014.
Equals A002981 + 1.
Sequence in context: A000942 A000207 A002986 this_sequence A000208 A079154 A101716
Adjacent sequences: A090657 A090658 A090659 this_sequence A090661 A090662 A090663
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Dec 15 2003
|
|
EXTENSIONS
|
Better description from Don Reble, Dec 20, 2003
Three more terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 20 2003
a(14) from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Jan 05 2004
|
|
|
Search completed in 0.002 seconds
|
