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 1-3 of 3 results.

A295310 a(n) = gcd(n, A062401(n)), where A062401(n) = phi(sigma(n)).

Original entry on oeis.org

1, 2, 1, 2, 1, 2, 1, 8, 3, 2, 1, 12, 1, 2, 1, 2, 1, 6, 1, 4, 1, 2, 1, 8, 5, 2, 1, 4, 1, 6, 1, 4, 1, 2, 1, 36, 1, 2, 3, 8, 1, 2, 1, 4, 3, 2, 1, 12, 1, 10, 3, 2, 1, 2, 1, 8, 1, 2, 1, 12, 1, 2, 3, 2, 1, 6, 1, 4, 1, 2, 1, 24, 1, 2, 15, 4, 1, 6, 1, 20, 1, 2, 1, 12, 1, 2, 1, 8, 1, 18, 1, 4, 1, 2, 1, 24, 1, 2, 3, 20, 1, 6, 1, 8, 1
Offset: 1

Views

Author

Antti Karttunen, Nov 22 2017

Keywords

Links

Crossrefs

Cf. A000010, A000203, A062401, A295301, A295311, A295312, A295313.

Programs

  • Mathematica
    Array[GCD[#, EulerPhi[DivisorSigma[1, #]]] &, 105] (* Michael De Vlieger, Nov 23 2017 *)
  • PARI
    a(n) = gcd(n, eulerphi(sigma(n))); \\ Michel Marcus, Nov 23 2017

Formula

a(n) = gcd(n, A000010(A000203(n))).

A295312 a(n) = A062401(n) / A295310(n) = phi(sigma(n)) / gcd(n, phi(sigma(n))).

Original entry on oeis.org

1, 1, 2, 3, 2, 2, 4, 1, 4, 3, 4, 1, 6, 4, 8, 15, 6, 4, 8, 3, 16, 6, 8, 2, 6, 6, 16, 6, 8, 4, 16, 9, 16, 9, 16, 2, 18, 8, 8, 3, 12, 16, 20, 6, 8, 12, 16, 5, 36, 6, 8, 21, 18, 16, 24, 4, 32, 12, 16, 4, 30, 16, 16, 63, 24, 8, 32, 9, 32, 24, 24, 4, 36, 18, 4, 12, 32, 8, 32, 3, 110, 18, 24, 8, 36, 20, 32, 6, 24, 4, 48, 12, 64, 24, 32, 3
Offset: 1

Views

Author

Antti Karttunen, Nov 22 2017

Keywords

Links

Crossrefs

Cf. A000010, A000203, A062401, A295301, A295310, A295311, A295315.

Programs

  • PARI
    a(n) = my(fsn = eulerphi(sigma(n))); fsn/gcd(n, fsn); \\ Michel Marcus, Nov 23 2017

Formula

a(n) = A000010(A000203(n)) / gcd(n, A000010(A000203(n))).

A295313 a(n) = gcd(sigma(n), phi(sigma(n))).

Original entry on oeis.org

1, 1, 2, 1, 2, 4, 4, 1, 1, 6, 4, 4, 2, 8, 8, 1, 6, 3, 4, 6, 16, 12, 8, 4, 1, 6, 8, 8, 2, 24, 16, 9, 16, 18, 16, 1, 2, 4, 8, 6, 6, 32, 4, 12, 6, 24, 16, 4, 3, 3, 24, 14, 18, 8, 24, 8, 16, 6, 4, 24, 2, 32, 8, 1, 12, 48, 4, 18, 32, 48, 24, 3, 2, 6, 4, 4, 32, 24, 16, 6, 11, 18, 12, 32, 36, 4, 8, 12, 6, 18, 16, 24, 64, 48, 8
Offset: 1

Views

Author

Antti Karttunen, Nov 22 2017

Keywords

Links

Crossrefs

Cf. A000010, A000203, A009195, A295311, A295314, A295315.

Programs

  • PARI
    a(n) = my(sn = sigma(n)); gcd(sn, eulerphi(sn)); \\ Michel Marcus, Nov 23 2017

Formula

a(n) = A009195(A000203(n)).
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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