A257559 The slowest increasing sequence of semiprimes with strictly increasing difference of successive terms.

4, 6, 9, 14, 21, 33, 46, 62, 82, 106, 133, 161, 194, 235, 278, 323, 371, 422, 478, 535, 597, 662, 731, 802, 878, 955, 1037, 1121, 1207, 1294, 1382, 1473, 1565, 1658, 1754, 1851, 1954, 2059, 2165, 2279, 2395, 2513, 2638, 2771, 2906, 3043

Offset: 1

Author

Zak Seidov, Apr 30 2015

Keywords

• nonn

Comments

Semiprime analog of A070865.

Heuristically a(n) is around n^2 log n/log log n. - Charles R Greathouse IV, May 01 2015

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001358, A070865.

Programs

PARI

issemi(n)=bigomega(n)==2
t=0; print1(last=4); while(1, n=last+t; while(!issemi(n++),); print1(", "n); t=n-last; last=n) \\ Charles R Greathouse IV, Apr 30 2015

Formula

a(n) >> n^2. - Charles R Greathouse IV, Apr 30 2015