|
|
A066828
|
|
Numbers k that divide the average of prime(k-1) and prime(k+1).
|
|
0
|
|
|
4, 5, 11, 12, 70, 72, 1053, 6459, 6460, 40083, 251742, 637320, 637322, 637330, 10553828, 69709721, 179992913, 179992922, 465769813, 1208198617, 1208198629, 3140421742, 3140421769, 3140421866, 8179002192, 8179002205, 8179002209
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Each cluster of candidates is about e (2.71828...) times as large as the previous one.
|
|
LINKS
|
|
|
EXAMPLE
|
The average of prime(4) = 7 and prime(6) = 13 is 10, which is divisible by 5, so 5 is a term of the sequence.
|
|
MATHEMATICA
|
a = 0; b = 1; c = 2; Do[ c = Prime[ n + 1 ]; If[ IntegerQ[ (a + c)/(2n) ], Print[ n ] ]; a = b; b = c, {n, 1, 2 10^9} ]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|