A350095 a(n) is the smaller of 2 consecutive primes bounding an interval containing a record number A350097(n) of odd squarefree semiprimes (A046388).

13, 31, 89, 199, 211, 887, 1129, 1327, 9973, 15683, 19609, 44293, 155921, 370261, 396733, 492113, 1357201, 1671781, 3826019, 17836409, 20831323, 47465267, 107534587, 122164747, 434865437, 436273009, 2300942549, 4302407359, 10726904659, 25056082087, 42652618343

Offset

1,1

Links

Lucas A. Brown, Table of n, a(n) for n = 1..32 (terms 1-28 from Hugo Pfoertner, 29-31 from Martin Ehrenstein)

Lucas A. Brown, Python program.

Formula

A350096(n) = nextprime(a(n)).

Example

a(1) = 13: semiprime 15 < 17 = nextprime(a(1)) = A350096(1);
a(2) = 31: semiprimes 33, 35 < 37 = A350096(2);
a(6) = 887: semiprimes 889, 893, 895, 899, 901, 905 < 907 = A350096(6);
a(7) = 1129: semiprimes 1133, 1135, 1137, 1139, 1141, 1145, 1147, 1149 < 1151 = A350096(7);
a(8) = 1327: semiprimes 1329, 1333, 1337, 1339, 1343, 1345, 1347, 1349, 1351, 1355, 1357 < 1361 = A350096(8).

Crossrefs

A350096 are the upper ends of the intervals, A350097 are the corresponding counts of odd squarefree semiprimes in the intervals.

Cf. A000101, A005250, A046388.

Sequence in context: A335732 A342706 A095379 * A160772 A271575 A039403

Adjacent sequences: A350092 A350093 A350094 * A350096 A350097 A350098

Keyword

nonn

Author

Hugo Pfoertner, Dec 25 2021

Extensions

a(29)-a(31) from Martin Ehrenstein, Dec 28 2021

a(32) from Lucas A. Brown, Mar 21 2024

Status

approved