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 1-4 of 4 results.

A296364 a(n) = A296349(n) - A030304(n).

Original entry on oeis.org

0, 0, 0, 3, 0, 7, 11, 11, 0, 16, 0, 28, 29, 37, 38, 31, 0, 37, 54, 43, 7, 49, 3, 83, 73, 90, 75, 104, 106, 104, 105, 79, 0, 86, 124, 93, 0, 154, 144, 107, 32, 121, 164, 168, 39, 131, 212, 207, 177, 215, 233, 210, 181, 231, 183, 267, 258, 276, 218, 281
Offset: 0

Views

Author

N. J. A. Sloane, Dec 16 2017

Keywords

Comments

Another measure of the binary "early-birdness" of n (cf. A296356, A116700).

Crossrefs

A083652 Sum of lengths of binary expansions of 0 through n.

Original entry on oeis.org

1, 2, 4, 6, 9, 12, 15, 18, 22, 26, 30, 34, 38, 42, 46, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 136, 142, 148, 154, 160, 166, 172, 178, 184, 190, 196, 202, 208, 214, 220, 226, 232, 238, 244, 250, 256, 262, 268, 274, 280, 286, 292
Offset: 0

Views

Author

Reinhard Zumkeller, May 01 2003

Keywords

Comments

a(n) = A001855(n) + 1 for n > 0;
a(0) = A070939(0)=1, n > 0: a(n) = a(n-1) + A070939(n).
A030190(a(k))=1; A030530(a(k)) = k + 1.
Partial sums of A070939. - Hieronymus Fischer, Jun 12 2012
Young writes "If n = 2^i + k [...] the maximum is (i+1)(2^i+k)-2^{i+1}+2." - Michael Somos, Sep 25 2012

Examples

			G.f. = 1 + 2*x + 4*x^2 + 6*x^3 + 9*x^4 + 12*x^5 + 15*x^6 + 18*x^7 + 22*x^8 + ...
		

Crossrefs

A296349 is an essentially identical sequence.

Programs

  • Haskell
    a083652 n = a083652_list !! n
    a083652_list = scanl1 (+) a070939_list
    -- Reinhard Zumkeller, Jul 05 2012
    
  • Mathematica
    Accumulate[Length/@(IntegerDigits[#,2]&/@Range[0,60])] (* Harvey P. Dale, May 28 2013 *)
    a[n_] := (n + 1) IntegerLength[n + 1, 2] - 2^IntegerLength[n + 1, 2] + 2;Table[a[n], {n, 0, 58}] (* Peter Luschny, Dec 02 2017 *)
  • PARI
    {a(n) = my(i); if( n<0, 0, n++; i = length(binary(n)); n*i - 2^i + 2)}; /* Michael Somos, Sep 25 2012 */
    
  • PARI
    a(n)=my(i=#binary(n++));n*i-2^i+2 \\ equivalent to the above
    
  • Python
    def A083652(n):
        s, i, z = 1, n, 1
        while 0 <= i: s += i; i -= z; z += z
        return s
    print([A083652(n) for n in range(0, 59)]) # Peter Luschny, Nov 30 2017
    
  • Python
    def A083652(n): return 2+(n+1)*(m:=(n+1).bit_length())-(1<Chai Wah Wu, Mar 01 2023

Formula

a(n) = 2 + (n+1)*ceiling(log_2(n+1)) - 2^ceiling(log_2(n+1)).
G.f.: g(x) = 1/(1-x) + (1/(1-x)^2)*Sum_{j>=0} x^2^j. - Hieronymus Fischer, Jun 12 2012; corrected by Ilya Gutkovskiy, Jan 08 2017
a(n) = A123753(n) - n. - Peter Luschny, Nov 30 2017

A341766 a(n) = difference between the starting positions of the first digit of the binary representation of n, where n starts at its natural position in the string, and the second occurrence of the same string in the binary Champernowne string (starting at 0) 011011100101110111100010011010... (cf. A030190).

Original entry on oeis.org

3, 1, 4, 1, 12, 4, 5, 1, 32, 13, 2, 9, 15, 5, 6, 1, 80, 36, 12, 31, 76, 8, 23, 21, 39, 16, 69, 11, 18, 6, 7, 1, 192, 91, 38, 85, 3, 45, 20, 73, 163, 67, 2, 22, 40, 3, 45, 49, 95, 43, 139, 37, 118, 31, 3, 25, 46, 19, 137, 13, 21, 7, 8, 1, 448, 218, 100, 211, 31, 136, 79, 197, 429, 25, 58, 123
Offset: 0

Views

Author

Scott R. Shannon, Feb 19 2021

Keywords

Comments

Consider the infinite string 011011100101110111100010011010... (cf. A030190) formed by the concatenation of all binary digits of all nonnegative numbers. From the position of the first digit of the binary representation of n, where n starts as its natural position in the string, find the number of digits one has to move forward to get to the start of the second occurrence of n. This is a(n).

Examples

			a(0) = 3 as '0' starts at position 1 and appears again at position 4.
a(1) = 1 as '1' starts at position 2 and appears again at position 3.
a(4) = 12 as '100' starts at position 7 and appears again at position 19.
a(7) = 1 as '111' starts at position 16 and appears again at position 17.
a(8) = 32 as '1000' starts at position 19 and appears again at position 51.
		

Crossrefs

Programs

  • Python
    def a(n):
        b = s = bin(n)[2:]
        while s.find(b, 1) < 0: n += 1; s += bin(n)[2:]
        return s.find(b, 1)
    print([a(n) for n in range(76)]) # Michael S. Branicky, Sep 16 2022

Formula

From Michael S. Branicky, Sep 16 2022: (Start)
a(2^k-1) = 1, for k >= 1;
a(2^k) = (k+1)*2^k, for k >= 0. (End)

A083655 Numbers which do not appear prematurely in the binary Champernowne word (A030190).

Original entry on oeis.org

0, 1, 2, 4, 8, 10, 16, 32, 36, 64, 128, 136, 256, 512, 528, 1024, 2048, 2080, 4096, 8192, 8256, 16384, 32768, 32896, 65536, 131072, 131328, 262144, 524288, 524800, 1048576, 2097152, 2098176, 4194304, 8388608, 8390656, 16777216, 33554432
Offset: 0

Views

Author

Reinhard Zumkeller, May 01 2003

Keywords

Comments

In other words, numbers k whose binary expansion first appears in A030190 at its expected place, i.e., n appears first starting at position A296349(n). - N. J. A. Sloane, Dec 17 2017
a(n) are the Base 2 "Punctual Bird" numbers: write the nonnegative integers, base 2, in a string 011011100101110111.... Sequence gives numbers which do not occur in the string ahead of their natural place. - Graeme McRae, Aug 11 2007

Crossrefs

A000079 is a subsequence.
For the complement, the "Early Bird" numbers, see A296365.

Programs

  • Mathematica
    LinearRecurrence[{0,0,6,0,0,-8},{0,1,2,4,8,10,16,32,36},50] (* Harvey P. Dale, Aug 19 2020 *)
  • PARI
    a(n)= if (n<=2, n, my (m=n\3); if (n%3==0, 2^(2*m), n%3==1, 2^(2*m+1), 2^m + 2^(2*m+1)))  \\ Rémy Sigrist, Jun 14 2020
    
  • PARI
    concat(0, Vec(x*(1 + 2*x + 4*x^2 + 2*x^3 - 2*x^4 - 8*x^5 - 8*x^6 - 8*x^7) / ((1 - 2*x^3)*(1 - 4*x^3)) + O(x^40))) \\ Colin Barker, Jun 14 2020
    
  • PARI
    a(n) = 2^((2*n+1)\3) + (n%3==2)<<(n\3) - (n<3) \\ Charles R Greathouse IV, Dec 16 2022

Formula

A083653(a(n))=a(n), A083654(a(n))=1.
a(0)=0, a(1)=1, a(2)=2; then for n>=1, a(3n)=2^(2n), a(3n+1)=2^(2n+1), a(3n+2)=2^(2n+1)+2^n. - Graeme McRae, Aug 11 2007
From Colin Barker, Jun 14 2020: (Start)
G.f.: x*(1 + 2*x + 4*x^2 + 2*x^3 - 2*x^4 - 8*x^5 - 8*x^6 - 8*x^7) / ((1 - 2*x^3)*(1 - 4*x^3)).
a(n) = 6*a(n-3) - 8*a(n-6) for n>8. (End)
a(n) = 2^floor(2*(n+2)/3-1) + (floor((n+1)/3)-floor(n/3))*2^(floor(n/3)) - floor(5/(n+3)). - Alan Michael Gómez Calderón, Dec 15 2022

Extensions

More terms from Graeme McRae, Aug 11 2007
Showing 1-4 of 4 results.