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A067837
a(1)=2; to form a(n+1), append P, the largest prime < a(n), if any and Q, the smallest prime > a(n), at the beginning and the end of a(n), respectively.
0
2, 23, 192329, 192323192329192341, 192323192329192339192323192329192341192323192329192399
OFFSET
1,1
EXAMPLE
To form a(2), note that there is no prime before 2 and that 3 is the prime coming immediately after 2. So a(2) = 23. To form a(3), the prime coming immediately before 23 is 19 and the prime coming immediate after 23 is 29. So a(3) = 192329.
CROSSREFS
Sequence in context: A369993 A114256 A110714 * A358384 A334616 A089987
KEYWORD
base,nonn
AUTHOR
Joseph L. Pe, Feb 11 2002
STATUS
approved