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 1-5 of 5 results.

A292373 A binary encoding of 3-digits in base-4 representation of n.

Original entry on oeis.org

0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 4, 4, 4, 5, 4, 4, 4, 5, 4, 4, 4, 5, 6, 6, 6, 7, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 3, 4, 4, 4, 5, 4, 4, 4, 5, 4
Offset: 0

Views

Author

Antti Karttunen, Sep 15 2017

Keywords

Examples

			   n      a(n)     base-4(n)  binary(a(n))
                  A007090(n)  A007088(a(n))
  --      ----    ----------  ------------
   1        0          1           0
   2        0          2           0
   3        1          3           1
   4        0         10           0
   5        0         11           0
   6        0         12           0
   7        1         13           1
   8        0         20           0
   9        0         21           0
  10        0         22           0
  11        1         23           1
  12        2         30          10
  13        2         31          10
  14        2         32          10
  15        3         33          11
  16        0        100           0
  17        0        101           0
  18        0        102           0
  19        1        103           1
		

Crossrefs

Programs

  • Python
    def A292373(n): return int(bin(n&n>>1)[:1:-2][::-1],2) # Chai Wah Wu, Jun 30 2022

Formula

a(n) = A059905(A048735(n)) = A059906(A213370(n)).
For all n >= 0, A000120(a(n)) = A160383(n).

A039005 Numbers whose base-4 representation has the same number of 1's and 3's.

Original entry on oeis.org

0, 2, 7, 8, 10, 13, 19, 27, 28, 30, 32, 34, 39, 40, 42, 45, 49, 52, 54, 57, 67, 75, 76, 78, 95, 99, 107, 108, 110, 112, 114, 119, 120, 122, 125, 128, 130, 135, 136, 138, 141, 147, 155, 156, 158, 160, 162, 167, 168, 170, 173, 177, 180, 182, 185, 193, 196, 198
Offset: 1

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Author

Keywords

Crossrefs

Cf. A004171 (subsequence).

A031466 Numbers whose base-4 representation has one fewer 0 than 3's.

Original entry on oeis.org

3, 7, 11, 13, 14, 23, 27, 29, 30, 39, 43, 45, 46, 51, 53, 54, 57, 58, 60, 79, 87, 91, 93, 94, 103, 107, 109, 110, 115, 117, 118, 121, 122, 124, 143, 151, 155, 157, 158, 167, 171, 173, 174, 179, 181, 182, 185, 186, 188, 199, 203, 205
Offset: 1

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Author

Keywords

Comments

Numbers n such that A160383(n) - A160380(n) = 1. - Robert Israel, Jun 05 2018

Crossrefs

Programs

  • Maple
    filter:= proc(n) local L;
      L:= convert(n,base,4);
      numboccur(3,L) - numboccur(0,L)=1
    end proc:
    select(filter, [$1..300]); # Robert Israel, Jun 05 2018
  • Mathematica
    Select[Range[210],DigitCount[#,4,0]==DigitCount[#,4,3]-1&] (* Harvey P. Dale, Dec 16 2011 *)

A039006 Numbers whose base-4 representation has the same number of 2's and 3's.

Original entry on oeis.org

0, 1, 4, 5, 11, 14, 16, 17, 20, 21, 27, 30, 35, 39, 44, 45, 50, 54, 56, 57, 64, 65, 68, 69, 75, 78, 80, 81, 84, 85, 91, 94, 99, 103, 108, 109, 114, 118, 120, 121, 131, 135, 140, 141, 147, 151, 156, 157, 175, 176, 177, 180, 181, 187, 190, 194, 198, 200, 201, 210
Offset: 1

Views

Author

Keywords

Crossrefs

Cf. A000302, A052539 (subsequences).

Programs

  • Mathematica
    Select[Range[0,250],DigitCount[#,4,2]==DigitCount[#,4,3]&] (* Harvey P. Dale, Mar 19 2017 *)

A338854 Product of the nonzero digits of (n written in base 4).

Original entry on oeis.org

1, 1, 2, 3, 1, 1, 2, 3, 2, 2, 4, 6, 3, 3, 6, 9, 1, 1, 2, 3, 1, 1, 2, 3, 2, 2, 4, 6, 3, 3, 6, 9, 2, 2, 4, 6, 2, 2, 4, 6, 4, 4, 8, 12, 6, 6, 12, 18, 3, 3, 6, 9, 3, 3, 6, 9, 6, 6, 12, 18, 9, 9, 18, 27, 1, 1, 2, 3, 1, 1, 2, 3, 2, 2, 4, 6, 3, 3, 6, 9, 1
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 12 2020

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Times @@ DeleteCases[IntegerDigits[n, 4], 0], {n, 0, 80}]
    nmax = 80; A[] = 1; Do[A[x] = (1 + x + 2 x^2 + 3 x^3) A[x^4] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
  • PARI
    a(n) = vecprod(select(x->x, digits(n, 4))); \\ Michel Marcus, Nov 12 2020

Formula

G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2 + 3*x^3) * A(x^4).
a(n) = 2^A160382(n) * 3^A160383(n).
Showing 1-5 of 5 results.