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.

A043283 Maximal run length in base-9 representation of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2
Offset: 1

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Author

Keywords

Crossrefs

Cf. A007095.
Cf. A043276-A043290 for base-2 to base-16 analogs.
Cf. A002452 (gives the positions of records, the first occurrence of each n).
Cf. also A044940.

Programs

  • Mathematica
    A043283[n_]:=Max[Map[Length,Split[IntegerDigits[n,9]]]];Array[A043283,100] (* Paolo Xausa, Sep 27 2023 *)
  • PARI
    A043283(n, b=9)={my(m, c=1); while(n>0, n%b==(n\=b)%b && c++ && next; m=max(m, c); c=1); m} \\ M. F. Hasler, Jul 23 2013

A044931 a(n) = so-se, where so(se)=sum of odd(even) base 9 run lengths of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, 2, 2, 2, 2, 2, 2, 2, 2, 2, -2, -1, 3, 3, 3, 3, 3, 3, 3, 3, -1, 3, -1, -1, -1, -1, -1, -1, -1, 3, 3
Offset: 1

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Examples

			From _Antti Karttunen_, Dec 16 2017: (Start)
For n = 82 = 1*(9^2) + 0*(9^1) + 1*(9^0), thus written as "101" in base 9, there are three odd runs (each of length 1) and no even runs, so a(82) = 3*1 = 3.
For n = 7383, "11113" in base 9, there is an even run of length 4 and an odd run of length 1, thus a(7383) = 1-4 = -3.
(End)
		

Crossrefs

Programs

  • Mathematica
    Array[Total[Length /@ #1] - Total[Length /@ Complement[#2, #1]] & @@ {Select[#, OddQ@ Length@ # &], #} &@ Split@ IntegerDigits[#, 9] &, 100] (* Michael De Vlieger, Dec 16 2017 *)
  • PARI
    A044931(n) = { my(rl=0, d, prev_d = -1, s=0); while(n>0, d = (n%9); n = ((n-d)/9); if(d==prev_d, rl++, s += ((-1)^rl)*rl; prev_d = d; rl = 1)); -(s + ((-1)^rl)*rl); }; \\ Antti Karttunen, Dec 16 2017

Extensions

More terms from Antti Karttunen, Dec 16 2017

A043536 Number of distinct base-9 digits of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 3, 3, 3, 3, 3, 3, 3, 2, 1, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 3, 3, 3, 3
Offset: 1

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Examples

			As 731 = 1*(9^3) + 0*(9^2) + 0*(9^1) + 2*(9^0), it is written in base 9 (A007095) as "1002". There are three kinds of digits present, thus a(731) = 3. - _Antti Karttunen_, Dec 22 2017
		

Crossrefs

Programs

Extensions

More terms from Antti Karttunen, Dec 22 2017

A044949 Number of runs of odd length in the base-9 representation of n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 0, 1, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 3, 3, 3, 3
Offset: 1

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Author

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Crossrefs

Programs

  • Mathematica
    Array[Count[Map[Length, Split@ IntegerDigits[#, 9]], ?OddQ] &, 105] (* _Michael De Vlieger, Dec 22 2017 *)
  • PARI
    A044949(n) = { my(rl=0, d, prev_d = -1, s=0); while(n>0, d = (n%9); n = ((n-d)/9); if(d==prev_d, rl++, s += (rl%2); prev_d = d; rl = 1)); (s + (rl%2)); }; \\ Antti Karttunen, Dec 22 2017

Formula

As 731 = 1*(9^3) + 0*(9^2) + 0*(9^1) + 2*(9^0), it is written in base 9 (A007095) as "1002". There is one run of even length, and two runs of length 1 (thus of odd length), thus a(731) = 2. - Antti Karttunen, Dec 22 2017

Extensions

More terms from Antti Karttunen, Dec 22 2017
Showing 1-4 of 4 results.