A050692 Largest prime factor of composite a(n) is a substring of a(n).

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

Offset

1,1

Comments

Includes 10^k*p if p is a prime >= 5 and k >= 1. - Robert Israel, Mar 13 2018

Links

Robert Israel, Table of n, a(n) for n = 1..10000

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

Cf. A050691, A050693.

Sequence in context: A325571 A366926 A102802 * A050693 A200046 A349750

Adjacent sequences: A050689 A050690 A050691 * A050693 A050694 A050695

Keyword

nonn,base

Author

Patrick De Geest, Aug 15 1999

Status

approved