A095393 Terms n are such that exactly half[=24] of the {210n+r} set is prime. Here r runs through the reduced residue system mod 210 (RRS[210]).

18, 19, 25, 33, 39, 42, 61, 65, 85, 86, 92, 100, 102, 112, 154, 175, 203, 259, 265, 281, 369, 380, 384, 441, 495, 518, 611, 649, 748, 840, 1083, 1355, 1376, 1515, 1559, 1610, 1703, 1874, 2226, 2355, 2464, 2667, 2716, 3371, 3577, 4011, 4021, 4791, 5290, 5808

Offset

1,1

Links

Table of n, a(n) for n=1..50.

Formula

In 210n+RRS[210] the number of primes is 24=phi[210]/2.

Example

For n=92269 the 24 primes are:
{19376491,19376501,19376503,19376507,19376521,19376527,19376543,19376563,
19376569,19376573,19376579,19376597,19376629,19376633,19376639,19376647,
19376653,19376657,19376663,19376671,19376677,19376683,19376689,19376699}

Mathematica

{k=0, u=0, ta=Table[0, {256}]}; Do[{m=0}; w=k; Do[s=210k+r; s1=210k+r+2; If[PrimeQ[s], m=m+1], {r, 1, 210}]; If[Equal[m, 24], Print[k]; ta[[u]]=k; u=u+1], {k, 0, 1000000}]

Crossrefs

Cf. A095389-A095392.

Sequence in context: A146331 A308894 A031956 * A301601 A056022 A118510

Adjacent sequences: A095390 A095391 A095392 * A095394 A095395 A095396

Keyword

nonn

Author

Labos Elemer, Jun 16 2004

Status

approved