login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A257559 The slowest increasing sequence of semiprimes with strictly increasing  difference of successive terms. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

FORMULA

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

PROG

(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

CROSSREFS

Cf. A001358, A070865.

Sequence in context: A175587 A175709 A073679 * A118689 A118692 A020706

Adjacent sequences:  A257556 A257557 A257558 * A257560 A257561 A257562

KEYWORD

nonn

AUTHOR

Zak Seidov, Apr 30 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 09:35 EDT 2019. Contains 322385 sequences. (Running on oeis4.)