login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A125025 Lengths of rows in A124570. 1
3, 8, 3, 8, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is to A124570 as A123556 is to A124064.

a(n) is at most A053669(n)^2, with equality if and only if A053669(n)^2 is the first semiprime in the corresponding arithmetic progression. - Charlie Neder, Jan 10 2019

By subsampling a given arithmetic progression with k terms and distance d one may generate an arithmetic progression of a larger distance d*b, b=1,2,3...., with 1+(k-1)/b terms: a(b*n) >= 1+floor( (a(n)-1)/b ), b=1,2,3..... - R. J. Mathar, Aug 02 2021

18 <= a(6) <= 24. - Jinyuan Wang, Aug 06 2021

a(12) >= 17.  a(18) >= 18.  a(24) >= 18.  a(30) >= 21.  a(36) >= 19.  a(42) >= 20. a(6006) >= 24 (starting 652744562555081).  Hugo van der Sanden, Aug 14 2021

LINKS

Table of n, a(n) for n=1..5.

CROSSREFS

Cf. A001358, A123556, A124064, A124570, A091016 (for n=6).

Sequence in context: A333287 A117240 A151857 * A309345 A010706 A204998

Adjacent sequences:  A125022 A125023 A125024 * A125026 A125027 A125028

KEYWORD

nonn,hard,more

AUTHOR

Jonathan Vos Post, Nov 15 2006

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 September 24 21:05 EDT 2021. Contains 347651 sequences. (Running on oeis4.)