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.

A092823 Euler numbers whose absolute value is prime.

Original entry on oeis.org

5, -61, -23489580527043108252017828576198947741
Offset: 1

Views

Author

Eric W. Weisstein, Mar 06 2004

Keywords

Comments

The next terms are known to be A122045(454) and A122045(510), but are too big to include (see A103234).

Links

Crossrefs

Cf. A000364, A014547, A103234, A122045.

Formula

a(n) = A122045(A103234(n)). - Amiram Eldar, Aug 26 2025

Extensions

Definition edited by N. J. A. Sloane, Sep 08 2020

A250220 Numbers k such that A241601(k) is prime.

Original entry on oeis.org

7, 9, 12, 16, 17, 18, 26, 34, 36, 38, 39, 42, 49, 74, 114, 118, 337, 396, 455
Offset: 1

Views

Author

Eric Chen, Dec 24 2014

Keywords

Comments

Is the sequence infinite?
No other terms < 500. - Jinyuan Wang, Apr 02 2020

Crossrefs

Cf. A241601, A249909, A246006, A112548, A092132, A103234.

Extensions

a(17)-a(19) from Jinyuan Wang, Apr 02 2020

A250290 Numbers k such that Euler(k) (A122045(k)) is a semiprime.

Original entry on oeis.org

8, 10, 14, 26, 30, 58, 78
Offset: 1

Views

Author

Eric Chen, Dec 24 2014

Keywords

Comments

No more terms <= 200.
k=7634 is a term, but it is not known to be the next term after 78. - Jeppe Stig Nielsen, May 12 2023

Examples

			a(2) = 10 so Euler(10) = 50521 = 19 * 2659 is a semiprime.

Links

Crossrefs

Cf. A103234, A122045.

Programs

  • PARI
    is(k) = k%2==0 && bigomega(eulerfrac(k))==2 \\ slow, from Jeppe Stig Nielsen, May 12 2023
Showing 1-3 of 3 results.

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

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