A124049 a(n) = c is least number such that 10^n/2 -/+ c are primes.

0, 3, 9, 81, 123, 57, 87, 243, 69, 63, 189, 231, 1569, 381, 231, 1443, 1113, 321, 339, 1353, 363, 519, 1323, 1503, 741, 1221, 957, 1053, 339, 5931, 2121, 2301, 2031, 4773, 4737, 10281, 1317, 129, 3873, 1443, 387, 11769, 8271, 5337, 2883, 7137, 8193, 8493

Offset

1,2

Comments

Related to Goldbach pairs of 10^n: a(n)=10^n/2 -A124450(n) Lesser of pair of closest primes whose sum is 10^n. Cf. A124013 Lesser of pair of most widely separated primes whose sum is 10^n, A065577 Number of Goldbach partitions of 10^n

All terms are divisible by 3 - see A108163.

Links

Table of n, a(n) for n=1..48.

Example

Next terms up to n = 101: 14637, 9897,
6471, 183, 8043, 6921,6699, 29127, 3663, 12537, 3777,
6741, 2253, 561, 3783, 26979, 16491, 6543, 10683,
1749, 6417, 38871, 22767, 62403, 8631, 4497, 20739,
453, 16731, 25293, 4341, 37467,
55323,4587,37083,24717,6687,8763,22551,29367,37881,14301,8637,34101,22179,26811,7059,1647

Mathematica

lnc[n_]:=Module[{c=0, t=10^n/2}, While[!AllTrue[t+{c, -c}, PrimeQ], c++]; c]; Array[ lnc, 50] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 21 2014 *)

Crossrefs

Cf. A065577, A124013, A124450.

Sequence in context: A000218 A139731 A259986 * A067623 A171557 A055156

Adjacent sequences: A124046 A124047 A124048 * A124050 A124051 A124052

Keyword

nonn

Author

Hans Havermann and Zak Seidov, Nov 03 2006

Status

approved