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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A215477 Semiprimes with consecutive (ascending) digits. 2
4, 6, 9, 34, 123, 789, 901, 1234, 34567, 56789, 901234, 1234567, 7890123, 567890123, 12345678901, 345678901234567, 4567890123456789, 12345678901234567, 890123456789012345, 3456789012345678901, 456789012345678901234, 123456789012345678901234567, 1234567890123456789012345678901, 23456789012345678901234567890123 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is to semiprimes A001358 as A006055 is to primes A000040.

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

a(9) = 34567 because it is semiprime 13 * 2659, and (3,4,5,6,7) are consecutive ascending digits.

CROSSREFS

Cf. A001358, A118697, A059043, A006055, A161760.

Sequence in context: A338378 A081614 A192220 * A292154 A291717 A303699

Adjacent sequences:  A215474 A215475 A215476 * A215478 A215479 A215480

KEYWORD

nonn,base,easy

AUTHOR

Jonathan Vos Post, Aug 12 2012

EXTENSIONS

Corrected and extended by R. J. Mathar, Aug 13 2012

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 November 30 03:48 EST 2021. Contains 349417 sequences. (Running on oeis4.)