A284253 - OEIS

%I #20 Mar 28 2021 07:01:26

%S 1,2,3,4,5,6,7,8,9,2,11,12,13,2,15,16,17,18,19,4,21,2,23,24,25,2,27,4,

%T 29,6,31,32,3,2,35,36,37,2,3,8,41,6,43,4,45,2,47,48,49,10,3,4,53,54,

%U 55,8,3,2,59,12,61,2,63,64,65,6,67,4,3,14,71,72,73,2,75,4,77,6,79,16,81,2,83,12,85,2,3,8,89,18,91,4,3,2,95,96,97,14,9,20,101,6

%N a(n) = n / A284252(n).

%H Antti Karttunen, <a href="/A284253/b284253.txt">Table of n, a(n) for n = 1..10001</a>

%F a(n) = n / A284252(n).

%t a[n_] := Block[{p = First /@ FactorInteger[n]}, n / SelectFirst[p, # > p[[1]]^2 &, 1]]; Array[a, 120] (* _Giovanni Resta_, Mar 24 2017 *)

%o (Scheme) (define (A284253 n) (/ n (A284252 n)))

%o (PARI) a(n) = if(n<2, return(1), my(f=factor(n)[, 1]); for(i=2, #f, if(f[i]>f[1]^2, return(f[i]))); return(1));

%o for(n=1, 151, print1(n/a(n),", ")) \\ _Indranil Ghosh_, after _David A. Corneth_, Mar 24 2017

%o (Python)

%o from sympy import primefactors

%o def a(n):

%o     pf = primefactors(n)

%o     if pf: min_pf2 = min(pf)**2

%o     for i in pf:

%o         if i > min_pf2: return i

%o     return 1

%o print([n//a(n) for n in range(1, 151)]) # _Indranil Ghosh_, Mar 24 2017

%Y Cf. A020639, A284252, A284254, A284255, A284256, A284257, A284258, A284259.

%K nonn

%O 1,2

%A _Antti Karttunen_, Mar 24 2017