A087430 Nonprimes n with gpf(n) > gpf(n+1), where gpf=A006530 (greatest prime factor).

14, 15, 26, 34, 35, 38, 39, 44, 49, 51, 55, 62, 63, 65, 69, 74, 76, 80, 86, 87, 94, 95, 99, 104, 111, 116, 118, 119, 122, 123, 124, 129, 134, 142, 143, 146, 152, 153, 155, 158, 159, 161, 164, 174, 183, 185, 186, 188, 194, 195, 202, 203, 206, 207, 209, 214, 215

Offset: 1

Author

Reinhard Zumkeller, Sep 02 2003

Keywords

• nonn

Comments

Subsequence of A070087.

Links

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

Crossrefs

Cf. A087429.

Programs

Maple

N:= 1000: # to get all terms < N
V:= Vector(N):
p:= 1:
do
  p:= nextprime(p);
  if p > N then break fi;
  V[[seq(k*p,k=1..N/p)]]:= p
od:
select(t -> V[t] > V[t+1] and not isprime(t), [$1..N-1]); # Robert Israel, Jul 03 2018

Mathematica

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