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.

A152081 Least prime divisor of terms of A152080.

Original entry on oeis.org

5, 7, 3, 7, 5, 3, 11, 3, 5, 7, 3, 11, 13, 3, 7, 3, 3, 5, 5, 3, 5, 3, 13, 17, 3, 7, 11, 5, 7, 5, 3, 3, 7, 5, 3, 11, 5, 5, 19, 7, 5, 29, 3, 3, 11, 5, 5, 7, 11, 3, 7, 29, 5, 3, 3, 19, 3, 3, 3, 13, 5, 7, 29, 7, 31, 3, 23, 17, 13, 13, 3, 19, 3, 3, 7, 3, 5, 7, 3, 11, 11, 29, 37
Offset: 1

Views

Author

Vladimir Shevelev, Nov 23 2008

Keywords

Crossrefs

Cf. A020639, A152080, A000625, A152021, A152022, A152023, A152078.

Programs

  • PARI
    a000695(n) = fromdigits(binary(n), 4);
lista(nn) = forcomposite(n=1, nn, if (isprime(a000695(n)), print1(factor(n)[1,1], ", "))); \\ Michel Marcus, Dec 18 2018

Formula

a(n) = A020639(A152080(n)). - Michel Marcus, Sep 24 2023

Extensions

More terms from Michel Marcus, Jun 02 2013
More terms from Michel Marcus, Dec 18 2018

A152082 Largest prime divisors of the terms of A152080.

Original entry on oeis.org

11, 11, 29, 13, 23, 13, 11, 19, 37, 29, 71, 23, 23, 109, 47, 41, 5, 83, 17, 157, 19, 53, 37, 29, 167, 11, 53, 5, 13, 19, 5, 229, 103, 151, 263, 73, 23, 163, 43, 17, 167, 29, 19, 41, 83, 17, 191, 139, 89, 109, 149, 37, 43, 73, 53, 59, 5, 379, 383, 89, 233, 167
Offset: 1

Views

Author

Vladimir Shevelev, Nov 23 2008

Keywords

Crossrefs

Cf. A000695, A152021, A152022, A152023, A152078, A152080.

Programs

  • Mathematica
    f[n_] := FromDigits[IntegerDigits[n, 2], 4]; pmax[n_] := FactorInteger[n][[-1, 1]]; pmax /@ Select[Range[1300], CompositeQ[#] && PrimeQ[f[#]] &] (* Amiram Eldar, Aug 31 2019 *)

Extensions

More terms from Amiram Eldar, Aug 31 2019
Showing 1-2 of 2 results.

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

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