OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
MATHEMATICA
a[n_] := Mod[FactorInteger[n][[1, 1]], 4]; Array[a, 100] (* Amiram Eldar, Apr 26 2022 *)
PROG
(PARI)
A020639(n) = if(1==n, n, vecmin(factor(n)[, 1]));
(Python)
from sympy import factorint
def a(n): return 1 if n==1 else (2 if n%2==0 else min(factorint(n))%4)
print([a(n) for n in range(1, 106)]) # Michael S. Branicky, Apr 26 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 26 2022
STATUS
approved