A379167 Table read by row, where T(n,k), n>0 and k>0, represents the smallest n-digit number that is the product of k distinct primes and is sandwiched between semiprime numbers, or -1 if no such number exists.

5, -1, 34, -1, 122, 186, 870, -1, 1042, 1146, 1190, 5610, -1, 10118, 10002, 10030, 10230, 39270, -1, 100462, 100158, 100030, 100122, 110670, 881790, -1, 1000478, 1000022, 1000010, 1000758, 1001130, 1009470, -1, 10000202, 10000258, 10000002, 10000218, 10001670, 10010910, 15825810

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Example

Smallest n-digit numbers m product of k distinct primes sandwiched between two semiprimes m-1 and m+1:
  n k    m-1,           m,               m+1
  1 1   4 = 2^2,      5 = 5,            6 = 2 * 3;
  2 2  33 = 3 * 11,  34 = 2 * 17,      35 = 5 * 7;
  3 3 185 = 5 * 37, 186 = 2 * 3 * 31, 187 = 11 * 17;
Table read by rows:
   5;
  -1,       34;
  -1,      122,      186,      870;
  -1,     1042,     1146,     1190,     5610;
  -1,    10118,    10002,    10030,    10230,    39270;
  -1,   100462,   100158,   100030,   100122,   110670,   881790;
  -1,  1000478,  1000022,  1000010,  1000758,  1001130,  1009470;
  -1, 10000202, 10000258, 10000002, 10000218, 10001670, 10010910, 15825810;
  ...

Crossrefs

Cf. A001358, A067885, A378627, A378097.

Sequence in context: A336600 A336599 A066833 * A334887 A039813 A160632

Adjacent sequences: A379164 A379165 A379166 * A379168 A379169 A379170

Keyword

sign,tabf,base

Author

Jean-Marc Rebert, Dec 17 2024

Status

approved