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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

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: A192542 A325571 A102802 * A050693 A200046 A171133

Adjacent sequences:  A050689 A050690 A050691 * A050693 A050694 A050695

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Aug 15 1999

STATUS

approved

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Last modified October 21 23:34 EDT 2021. Contains 348160 sequences. (Running on oeis4.)