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.

A078154 Primes of the form A004154(k) + 1.

Original entry on oeis.org

2, 3, 7, 13, 73, 871782913, 1307674369, 62044840173323943937, 33078854415193864122595302822125378214568325182093497117061192683541123570097156545925087233
Offset: 1

Views

Author

Cino Hilliard, Dec 23 2002

Keywords

Comments

More precisely, scan A004154, add 1 and record the answer if it is a prime. The sequence may not be monotonic.
The next term is too large to include.

Links

Crossrefs

Cf. A004154, A078203, A078190, A078305.

Programs

  • Magma
    [a: n in [1..100] | IsPrime(a) where a is Factorial(n) div 10^Valuation(Factorial(n), 5)+1]; // Vincenzo Librandi, Jun 03 2016

Extensions

More terms from Joshua Zucker, Jan 11 2006

A078203 Numbers k such that A004154(k) + 1 is prime.

Original entry on oeis.org

1, 2, 3, 5, 6, 14, 15, 24, 74, 191, 222, 276, 2200, 3041, 3701, 4324, 6201
Offset: 1

Views

Author

Cino Hilliard, Dec 23 2002

Keywords

Crossrefs

Cf. A004154, A078154, A078190, A078305.

Programs

  • Mathematica
    f[n_] := n!/10^Sum[ Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ f[n] + 1], Print[n]], {n, 1, 850}]

Extensions

Extended by Joshua Zucker, Robert G. Wilson v and Jason Earls, Dec 24 2002
a(13) from Don Reble, Jan 12 2006
a(14)-a(17) from Michael S. Branicky, Jul 23 2023

A078305 Numbers k such that A004154(k) - 1 is prime.

Original entry on oeis.org

3, 4, 5, 6, 7, 13, 14, 19, 20, 28, 37, 99, 100, 108, 141, 304, 442, 682, 3641, 4076
Offset: 1

Views

Author

Cino Hilliard, Dec 23 2002

Keywords

Comments

Some of the larger entries may only correspond to probable primes.

Crossrefs

Cf. A004154, A078154, A078203, A078190.

Programs

  • Mathematica
    f[n_] := n!/10^Sum[ Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ f[n] - 1], Print[n]], {n, 1, 750}]

Extensions

Extended by Robert G. Wilson v and Jason Earls, Dec 24 2002
a(19)-a(20) from Michael S. Branicky, Jul 23 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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