A087430 - OEIS

%I #11 Jul 03 2018 21:22:01

%S 14,15,26,34,35,38,39,44,49,51,55,62,63,65,69,74,76,80,86,87,94,95,99,

%T 104,111,116,118,119,122,123,124,129,134,142,143,146,152,153,155,158,

%U 159,161,164,174,183,185,186,188,194,195,202,203,206,207,209,214,215

%N Nonprimes n with gpf(n) > gpf(n+1), where gpf=A006530 (greatest prime factor).

%C Subsequence of A070087.

%H Robert Israel, <a href="/A087430/b087430.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 1000: # to get all terms < N

%p V:= Vector(N):

%p p:= 1:

%p do

%p   p:= nextprime(p);

%p   if p > N then break fi;

%p   V[[seq(k*p,k=1..N/p)]]:= p

%p od:

%p select(t -> V[t] > V[t+1] and not isprime(t), [$1..N-1]); # _Robert Israel_, Jul 03 2018

%t With[{nn=250},Select[Complement[Range[nn],Prime[Range[PrimePi[ nn]]]], FactorInteger[ #][[-1,1]]>FactorInteger[#+1][[-1,1]]&]] (* _Harvey P. Dale_, Jul 14 2016 *)

%Y Cf. A087429.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Sep 02 2003