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.

A036215 Binary reversal of 3^n.

Original entry on oeis.org

1, 3, 9, 27, 69, 207, 621, 3345, 4275, 25497, 38247, 229173, 589185, 1669443, 5205897, 14045019, 34319397, 102566511, 307313949, 1843835217, 2312645619, 13776780249, 20417442711, 112792132341, 290155405761, 847524815523, 2611222884297, 7627711248315
Offset: 0

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Keywords

Comments

Compute 3^n in binary, reverse the bits, from 0 to the most significant bit of the power.

Crossrefs

Cf. A036213 and A036214.

Programs

  • Mathematica
    Table[FromDigits[Reverse[IntegerDigits[3^n, 2]], 2], {n, 0, 30}] (* Vincenzo Librandi, Sep 09 2013 *)
  • PARI
    a(n) = subst(Polrev(binary(3^n)), x, 2); \\ Michel Marcus, Sep 08 2013

Formula

a(n) = A030101(A000244(n)). - Michel Marcus, Sep 08 2013

Extensions

More terms from Michel Marcus, Sep 08 2013

A036214 Bit-reversing masks for 2*n bits.

Original entry on oeis.org

0, 18, 4740, 17966088, 1136090292240, 1171507928472027168, 19496308761789043518734400, 5212738348288268369644435170918528, 22344471816287582119092726913736555148345600, 1533995044405866391626076022957811770200509055768723968
Offset: 0

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Author

Keywords

References

  • R. Schroeppel: DECsystem-10/20 Processor Reference Manual AA-H391A-TK, Chapter 2, User Operations, section 2.15: Programming Examples: Reversing Order of Digits.

Crossrefs

Programs

  • Mathematica
    Table[2^n*(2^(2*n^2 + 3*n + 1) + 2^(2*n^2 + 2*n) - 2^(3*n + 1) - 1)/(2^(2*n + 1) - 1), {n, 0, 10}] (* Wesley Ivan Hurt, Jun 10 2024 *)
  • PARI
    A036214(n) = 2^n * ( 2^(2*n^2+3*n+1) + 2^(2*n^2+2*n) - 2^(3*n+1) - 1 ) / (2^(2*n+1) - 1); \\ Antti Karttunen, Jan 14 2024

Formula

a(n) = 2^n * ( 2^(2*n^2+3*n+1) + 2^(2*n^2+2*n) - 2^(3*n+1) - 1 ) / (2^(2*n+1) - 1).
log(a(n)) ~ log(4) * n ^ 2. - Bill McEachen, Jul 13 2024
Showing 1-2 of 2 results.