A345061 a(n) = gcd(A071324(n), A206369(n)).

1, 1, 2, 3, 4, 2, 6, 5, 7, 2, 10, 2, 12, 2, 4, 11, 16, 1, 18, 12, 4, 2, 22, 2, 21, 2, 20, 18, 28, 2, 30, 21, 4, 2, 8, 1, 36, 2, 4, 4, 40, 4, 42, 30, 4, 2, 46, 2, 43, 1, 4, 36, 52, 20, 8, 2, 4, 2, 58, 8, 60, 2, 2, 43, 8, 4, 66, 48, 4, 6, 70, 7, 72, 2, 2, 54, 12, 8, 78, 4, 61, 2, 82, 18, 8, 2, 4, 10, 88, 4, 12, 66

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Formula

a(n) = gcd(A071324(n), A206369(n)).

a(n) = gcd(A071324(n), A345060(n)) = gcd(A206369(n), A345060(n)).

a(n) = A071324(n) / A345062(n) = A206369(n) / A345063(n).

Mathematica

{1}~Join~Array[GCD[Total[-#*(-1)^Range[Length[#], 1, -1]] &@ Divisors[#], Times @@ (Sum[(-1)^(#2 - k)*#1^k, {k, 0, #2}] & @@@ FactorInteger[#])] &, 91, 2] (* Michael De Vlieger, Jul 06 2021, after Amiram Eldar at A071324 and A206369 *)

Prog

(PARI)
A071324(n) = my(d=Vecrev(divisors(n))); sum(k=1, #d, (-1)^(k+1)*d[k]); \\ From A071324
A206369(n) = sumdiv(n, d, eulerphi(n/d) * issquare(d)); \\ From A206369
A345061(n) = gcd(A071324(n), A206369(n));

Crossrefs

Cf. A071324, A206369, A345060, A345062, A345063.

Sequence in context: A299439 A109746 A286365 * A061020 A206369 A152958

Adjacent sequences: A345058 A345059 A345060 * A345062 A345063 A345064

Keyword

nonn

Author

Antti Karttunen, Jun 07 2021

Status

approved