A073863 a(1) = 4; a(n) = average of the largest and the smallest n-digit primes.

4, 54, 549, 5491, 54999, 549993, 5499997, 55000004, 549999972, 5499999987, 54999999998, 549999999996, 5500000000005, 55000000000005, 550000000000010, 5499999999999987, 55000000000000029, 549999999999999996

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Example

a(3) = (997 + 101)/2 = 549.

Maple

a:=n->(nextprime(10^n-1)+prevprime(10^(n+1)))/2: seq(a(n), n=1..20); # Emeric Deutsch, Feb 25 2005

Crossrefs

Sequence in context: A269507 A302942 A292305 * A269480 A199022 A221395

Adjacent sequences: A073860 A073861 A073862 * A073864 A073865 A073866

Keyword

base,nonn

Author

Amarnath Murthy, Aug 15 2002

Extensions

Corrected and extended by Emeric Deutsch, Feb 25 2005

Status

approved