login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103607 Write down the semiprimes but omit any semiprime (such as 46 or 69) that is the concatenation of consecutive semiprimes. 0
4, 6, 9, 10, 14, 15, 21, 22, 25, 26, 33, 34, 35, 38, 39, 49, 51, 55, 57, 58, 62, 65, 74, 77, 82, 85, 86, 87, 91, 93, 94, 95, 106, 111, 115, 118, 119, 121, 122, 123, 129, 133, 134, 141, 142, 143, 145, 146, 155, 158, 159, 161, 166, 169, 177, 178, 183, 185, 187 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The complement of this sequence is the sequence of semiprimes which are concatenations of successive semiprimes.
Note that this sequence is not analogous to A119615 for two reasons. In A119615 partial concatenation is taken into account, i.e., the terms 7, 11 prevent 71 to be included, while here only full concatenation is considered (hence 58, 62 do not forbid 86). Moreover in A119615 the terms to be concatenated are those in the sequence itself, while here are all the semiprimes. - Giovanni Resta, Jun 16 2016
LINKS
EXAMPLE
46 is not a term because concatenate(sp(1),sp(2)) = 46 = 2 * 23.
69 is not a term because concatenate(sp(2),sp(3)) = 69 = 3 * 23.
469 is not a term because concatenate(sp(1),sp(2),sp(3)) = 469 = 7 * 67.
1415 is not a term because concatenate(sp(5),sp(6)) = 1415 = 5 * 283.
2122 is not a term because concatenate(sp(7),sp(8)) = 2122 = 2 * 1061.
3839 is not a term because concatenate(sp(14),sp(15)) = 3839 = 11 * 349.
469101415 is not a term because concatenate(sp(1),sp(2),sp(3),sp(4)),sp(5),sp(6)) = 469101415 = 5 * 93820283.
Where sp(i) is A001358(i).
CROSSREFS
Sequence in context: A193801 A129336 A226526 * A264815 A351096 A108574
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Jun 07 2006
EXTENSIONS
Name edited by Giovanni Resta, Jun 16 2016
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 15 22:54 EDT 2024. Contains 374334 sequences. (Running on oeis4.)