A348940 a(n) = gcd(n, A326042(n)), where A326042 is multiplicative function A064989(sigma(A003961(n))).

1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 11, 1, 2, 1, 2, 1, 2, 3, 4, 1, 2, 5, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 3, 2, 1, 3, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 4, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 6, 1, 4, 1

Offset

1,6

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Formula

a(n) = gcd(n, A326042(n)).

a(n) = gcd(n, A348736(n)) = gcd(A326042(n), A348736(n));

a(n) = n / A348941(n) = A326042(n) / A348942(n).

Mathematica

f1[2, e_] := 1; f1[p_, e_] := NextPrime[p, -1]^e; s[n_] := Times @@ f1 @@@ FactorInteger[n]; f[p_, e_] := s[((q = NextPrime[p])^(e + 1) - 1)/(q - 1)]; s2[1] = 1; s2[n_] := Times @@ f @@@ FactorInteger[n]; a[n_] := GCD[n, s2[n]]; Array[a, 100] (* Amiram Eldar, Nov 05 2021 *)

Prog

(PARI)
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};
A326042(n) = A064989(sigma(A003961(n)));
A348940(n) = gcd(n, A326042(n));

Crossrefs

Cf. A326042, A348736, A348941, A348942.

Sequence in context: A174435 A330749 A294883 * A088530 A058060 A338160

Adjacent sequences: A348937 A348938 A348939 * A348941 A348942 A348943

Keyword

nonn

Author

Antti Karttunen, Nov 04 2021

Status

approved