|
|
A098424
|
|
Number of prime triples (p,q,r) <= n with p<q<r=p+6.
|
|
4
|
|
|
0, 0, 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 11
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,7
|
|
COMMENTS
|
Convention: a prime triple is <= n iff its smallest member is <= n;
|
|
LINKS
|
|
|
EXAMPLE
|
a(15) = #{(5,7,11),(7,11,13),(11,13,17),(13,17,19)} = 4.
|
|
MATHEMATICA
|
With[{pts=Select[Partition[Prime[Range[1200]], 3, 1], Last[#]-First[#] == 6&]}, Table[Count[pts, _?(First[#]<=n&)], {n, 110}]] (* Harvey P. Dale, Nov 09 2011 *)
|
|
PROG
|
(Haskell)
a098424 n = length [(p, q, r) | p <- takeWhile (<= n) a000040_list,
let r = p + 6, a010051 r == 1, q <- [p+1..r-1], a010051 q == 1]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|