A100393 Composite numbers k such that Gpf(k-1) < Gpf(k) > Gpf(k+1), where Gpf = A006530.

26, 34, 49, 51, 55, 65, 69, 76, 86, 94, 99, 111, 116, 118, 122, 129, 134, 142, 146, 155, 161, 183, 185, 188, 202, 206, 209, 214, 218, 237, 244, 246, 249, 254, 265, 267, 274, 287, 291, 295, 298, 302, 305, 309, 321, 326, 329, 334, 339, 341, 344, 351, 356, 362

Offset: 1

Author

Labos Elemer, Dec 14 2004

Keywords

• nonn

Comments

A006530(k) is the largest prime factor of k.

Examples

			26 is in the sequence because the largest prime factors of 25, 26, and 27 are 5, 13, and 3, respectively.
		

Links

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

Crossrefs

Cf. A006530, A100390, A100392.

Programs

Maple

gpf:= n -> max(numtheory:-factorset(n)):
L:= map(gpf, [$1..1000]):
select(t -> L[t]<> t and L[t]>L[t-1] and L[t]>L[t+1], [$2..nops(L)-1]); # Robert Israel, Jul 12 2018

Mathematica

<?(#[[1]]< #[[2]]> #[[3]]&),1,Heads->False]],CompositeQ[#+1]&]+1 (* _Harvey P. Dale, May 10 2022 *)

Extensions

Edited by Don Reble, Jun 13 2007