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!)
A050692 Largest prime factor of composite a(n) is a substring of a(n). 3
15, 25, 32, 36, 45, 50, 70, 75, 110, 125, 128, 130, 135, 147, 150, 170, 175, 190, 225, 230, 243, 250, 256, 290, 310, 324, 370, 375, 378, 384, 405, 410, 430, 432, 450, 470, 500, 512, 530, 540, 567, 590, 610, 625, 670, 672, 675, 700, 710, 730, 735, 750, 756 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Includes 10^k*p if p is a prime >= 5 and k >= 1. - Robert Israel, Mar 13 2018
LINKS
EXAMPLE
E.g. 175 = 1{7}5 = 5.5.{7}.
MAPLE
filter:= proc(n) local p;
if isprime(n) then return false fi;
p:= max(numtheory:-factorset(n));
StringTools:-Search(convert(p, string), convert(n, string))<>0
end proc:
select(filter, [$2..1000]); # Robert Israel, Mar 13 2018
MATHEMATICA
d[n_]:=IntegerDigits[n]; t={}; Do[y=d[Max@@First/@FactorInteger[n]]; If[!PrimeQ[n]&&MemberQ[Partition[d[n], Length[y], 1], y], AppendTo[t, n]], {n, 2, 760}]; t (* Jayanta Basu, May 30 2013 *)
CROSSREFS
Sequence in context: A325571 A366926 A102802 * A050693 A200046 A349750
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Aug 15 1999
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 April 17 08:35 EDT 2024. Contains 371763 sequences. (Running on oeis4.)