A363082 - OEIS

A363082

Numbers k neither squarefree nor prime power such that q*r > k, where q = A053669(k) is the smallest prime that does not divide k and r = A007947(k) is the squarefree kernel.

12, 18, 20, 24, 28, 44, 52, 60, 68, 76, 84, 90, 92, 116, 120, 124, 126, 132, 140, 148, 150, 156, 164, 168, 172, 180, 188, 198, 204, 212, 220, 228, 234, 236, 244, 260, 264, 268, 276, 284, 292, 306, 308, 312, 316, 332, 340, 342, 348, 356, 364, 372, 380, 388, 404, 408, 412, 414, 420

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Michael De Vlieger, Plot b(n) = A126706(n) at (x, y) for n = ym + x = 1..1032256, m = 1016 and x = 1..m, y = 0..m-1, showing b(n) in A360765 in white, and b(n) in this sequence in other colors, where red indicates b(n) also in A360767, and blue indicates b(n) also in A360768.

FORMULA

This sequence is A126706 \ A360765.

EXAMPLE

a(1) = 12 since 12 is the smallest number that is neither squarefree nor a prime power. Additionally, 12 < 5*6.

a(2) = 18 since it is in A126706, and like 12, 18 < 5*6.

a(3) = 20 since it is neither squarefree nor prime power, and 20 < 3*10.

36 is not in this sequence since 36 > 5*6.

40 is not in this sequence since 40 > 3*10, etc.

MATHEMATICA

Select[Select[Range[452], Nor[PrimePowerQ[#], SquareFreeQ[#]] &], Function[{k, f}, Function[{q, r}, q r > k] @@ {SelectFirst[Prime@ Range[PrimePi[f[[-1, 1]]] + 1], ! Divisible[k, #] &], Times @@ f[[All, 1]]} ] @@ {#, FactorInteger[#]} &]

CROSSREFS

Cf. A007947, A053669, A126706, A360765, A360767, A360768.

Sequence in context: A345381 A328930 A364996 * A270660 A173490 A005101

Adjacent sequences: A363079 A363080 A363081 * A363083 A363084 A363085

KEYWORD

nonn

AUTHOR

Michael De Vlieger, Jul 29 2023

STATUS

approved