|
Search: id:A145173
|
|
|
| A145173 |
|
Least a(n) such that p(n)#*(p(n)#-a(n))-1 is prime with p(i)#=i-th primorial. |
|
+0
2
|
|
| 0, 1, 2, 1, 2, 4, 2, 1, 4, 9, 1, 2, 14, 2, 3, 9, 2, 9, 24, 1, 25, 1, 7, 8, 2, 52, 14, 13, 42, 7, 22, 8, 5, 20, 36, 9, 8, 10, 36, 56, 2, 14, 42, 7, 2, 128, 159, 45, 49, 1, 16, 69, 211, 80, 19, 13, 3, 12, 25, 21, 106, 32, 39, 26, 21, 23, 5, 22, 66, 43, 45, 139, 350, 38, 26, 145, 19, 142
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
As n increases the sum a(n) for i=1 to n tends to n*(n+1)/2.
|
|
LINKS
|
Pierre CAMI, Table of n, a(n) for n = 1..704
|
|
EXAMPLE
|
2*(2-0-1=3 prime so a(1)=0 2*3*(2*3-1)-1=29 prime so a(2)=1 2*3*5*(2*3*5-2)-1=839 prime so a(3)=2
|
|
PROGRAM
|
(PARI) { allocatemem(932245000); default(primelimit, 4294965247); n=0; p=1; q=1; until (0, n=n+1; p=nextprime(p+1); q=q*p; for (a=0, 1000000000, r=q*(q-a)-1; if (isprime(r), print(n, " ", a); write("b145173.txt", n, " ", a); break; ); ) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jan 14 2009]
|
|
CROSSREFS
|
Cf. A144946, A144947
Sequence in context: A164281 A082693 A097082 this_sequence A082793 A114929 A152251
Adjacent sequences: A145170 A145171 A145172 this_sequence A145174 A145175 A145176
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Pierre CAMI (pierrecami(AT)tele2.fr), Oct 03 2008
|
|
EXTENSIONS
|
Corrected by several correspondents, Jan 14 2009
|
|
|
Search completed in 0.002 seconds
|
