A358757 - OEIS

%I #16 Dec 05 2023 10:55:46

%S 6,12,18,24,36,42,48,54,66,72,78,84,96,102,108,114,126,132,138,144,

%T 156,162,168,174,186,192,198,204,210,216,222,228,234,246,252,258,264,

%U 276,282,288,294,306,312,318,324,336,342,348,354,366,372,378,384,396,402,408,414,420,426,432,438,444,456

%N Numbers k such that the smallest prime that does not divide them is of the form 6m-1.

%C Numbers k such that A053669(k) is in A007528.

%C The asymptotic density of this sequence is Sum_{p prime, p == 5 (mod 6)} ((p-1)/(Product_{q prime, q <= p} q)) = 0.1376937818... . - _Amiram Eldar_, Dec 04 2022

%H Robert Israel, <a href="/A358757/b358757.txt">Table of n, a(n) for n = 1..10000</a>

%p filter:= proc(n) local p;

%p  p:= 3;

%p  do

%p    p:= nextprime(p);

%p    if n mod p <> 0 then return (p mod 6 = 5) fi

%p  od

%p end proc:

%p select(filter, [seq(i,i=6..1000,6)]); # _Robert Israel_, Dec 04 2023

%t f[n_] := Module[{p = 2}, While[Divisible[n, p], p = NextPrime[p]]; p]; Select[Range[500], Mod[f[#], 6] == 5 &] (* _Amiram Eldar_, Dec 04 2022 *)

%o (PARI) isA358757(n) = A358755(n);

%Y Cf. A007528, A053669, A358755 (characteristic function), A358756.

%Y Differs from A353530 for the first time at n=29, where a(29) = 210, which is not present in A353530.

%K nonn

%O 1,1

%A _Antti Karttunen_, Dec 03 2022