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.

A104089 Largest prime <= 4^n.

Original entry on oeis.org

3, 13, 61, 251, 1021, 4093, 16381, 65521, 262139, 1048573, 4194301, 16777213, 67108859, 268435399, 1073741789, 4294967291, 17179869143, 68719476731, 274877906899, 1099511627689, 4398046511093, 17592186044399, 70368744177643
Offset: 1

Views

Author

Cino Hilliard, Mar 03 2005

Keywords

Crossrefs

Cf. A014234, A104082, A104088, A104090-A104094, A003618, A104096.
Cf. A000040, A000302, A007917.

Programs

  • Mathematica
    NextPrime[4^Range[30], -1] (* Paolo Xausa, Oct 28 2024 *)
  • PARI
    g(n,b) = for(x=0,n,print1(precprime(b^x)","))

Formula

a(n) = A007917(A000302(n)). - Paolo Xausa, Oct 28 2024

A013605 a(n) = 5^n-prevprime(5^n).

Original entry on oeis.org

2, 2, 12, 6, 4, 6, 4, 44, 16, 6, 12, 12, 52, 2, 4, 62, 16, 102, 16, 26, 54, 54, 36, 38, 64, 2, 12, 42, 16, 102, 18, 72, 42, 68, 256, 18, 52, 84, 234, 54, 34, 72, 274, 266, 36, 14, 4, 56, 162, 2, 24, 122, 6, 14, 94, 446, 72, 56, 298, 384, 28, 26
Offset: 1

Views

Author

James Kilfiger (mapdn(AT)csv.warwick.ac.uk)

Keywords

Links

Crossrefs

Cf. A000351, A104090.

Programs

  • Maple
    seq(5^i-prevprime(5^i),i=1..100);
  • Mathematica
    #-NextPrime[#,-1]&/@(5^Range[70])  (* Harvey P. Dale, Mar 12 2011 *)
  • PARI
    a(n) = 5^n - precprime(5^n-1); \\ Michel Marcus, Aug 14 2019

A204578 Primes of the form 5^k-2.

Original entry on oeis.org

3, 23, 6103515623, 1490116119384765623, 88817841970012523233890533447265623, 11754943508222875079687365372222456778186655567720875215087517062784172594547271728515623, 44841550858394146269559346665277316200968382140048504696226185084473314645947539247572422027587890623
Offset: 1

Views

Author

M. F. Hasler, Jan 30 2012

Keywords

Comments

See the sequence A109080 for the corresponding exponents k.
The number a(3) = 6103515623 is also in A095304, A104090 and A128472.

Crossrefs

Cf. A109080.

Programs

  • PARI
    for(i=0,999, ispseudoprime(t=5^i-2) & print1(t","))

Formula

a(n) = 5^A109080(n)-2.
Showing 1-3 of 3 results.

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

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