cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A326192 Lexicographically earliest sequence such that for all i, j, a(i) = a(j) => A009195(i) = A009195(j) and f(i) = f(j), where f(n) = gcd(n,sigma(n)) * (-1)^[gcd(n,sigma(n))==n] and A009195(n) = gcd(n, phi(n)).

Original entry on oeis.org

1, 2, 2, 3, 2, 4, 2, 5, 6, 7, 2, 8, 2, 7, 9, 10, 2, 11, 2, 12, 6, 7, 2, 13, 14, 7, 15, 16, 2, 17, 2, 18, 9, 7, 2, 19, 2, 7, 6, 20, 2, 21, 2, 8, 22, 7, 2, 23, 24, 25, 9, 12, 2, 26, 14, 27, 6, 7, 2, 28, 2, 7, 15, 29, 2, 17, 2, 12, 9, 7, 2, 30, 2, 7, 14, 8, 2, 21, 2, 31, 32, 7, 2, 33, 2, 7, 9, 34, 2, 35, 36, 8, 6, 7, 37, 38, 2, 39, 22, 40, 2, 17, 2, 41, 22
Offset: 1

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Author

Antti Karttunen, Aug 24 2019

Keywords

Comments

Restricted growth sequence transform of the ordered pair [A009195(n), A326193(n)].
For all i, j:
A305800(i) = A305800(j) => a(i) = a(j),
a(i) = a(j) => A300242(i) = A300242(j),
a(i) = a(j) => A326196(i) = A326196(j).

Crossrefs

Programs

  • PARI
    up_to = 65537;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    Aux326192(n) = { my(u=gcd(n,sigma(n))); [gcd(n,eulerphi(n)), u*((-1)^(u==n))]; };
    v326192 = rgs_transform(vector(up_to, n, Aux326192(n)));
    A326192(n) = v326192[n];

A327163 Lexicographically earliest sequence such that for all i, j, a(i) = a(j) => f(i) = f(j), where f(n) = gcd(n,usigma(n)) * (-1)^[gcd(n,usigma(n))==n], and usigma is the sum of unitary divisors of n (A034448).

Original entry on oeis.org

1, 2, 2, 2, 2, 3, 2, 2, 2, 4, 2, 5, 2, 4, 6, 2, 2, 7, 2, 8, 2, 4, 2, 9, 2, 4, 2, 5, 2, 7, 2, 2, 6, 4, 2, 4, 2, 4, 2, 4, 2, 7, 2, 5, 10, 4, 2, 5, 2, 4, 6, 4, 2, 7, 2, 11, 2, 4, 2, 12, 2, 4, 2, 2, 2, 7, 2, 4, 6, 4, 2, 13, 2, 4, 2, 5, 2, 7, 2, 4, 2, 4, 2, 5, 2, 4, 6, 5, 2, 14, 15, 5, 2, 4, 16, 9, 2, 4, 6, 8, 2, 7, 2, 4, 6
Offset: 1

Views

Author

Antti Karttunen, Aug 28 2019

Keywords

Comments

Restricted growth sequence transform of function f, defined as f(n) = -A323166(n) = -n when n is one of unitary multiply-perfect numbers (A327158), otherwise f(n) = A323166(n) = gcd(n,A034448(n))
For all i, j:
A305800(i) = A305800(j) => a(i) = a(j) => A327164(i) = A327164(j).

Crossrefs

Programs

  • PARI
    up_to = 87360;
    rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A034448(n) = { my(f=factorint(n)); prod(k=1, #f~, 1+(f[k, 1]^f[k, 2])); }; \\ After code in A034448
    A323166(n) = gcd(n, A034448(n));
    Aux327163(n) = { my(u=A323166(n)); u*((-1)^(u==n)); };
    v327163 = rgs_transform(vector(up_to, n, Aux327163(n)));
    A327163(n) = v327163[n];
Showing 1-2 of 2 results.