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.

Previous Showing 21-30 of 239 results. Next

A353116 Base-8 representation of A000422(n).

Original entry on oeis.org

1, 25, 501, 10341, 152061, 2375761, 35145661, 516277661, 7267464261, 121672446261, 20125401442261, 3342313131342261, 564731226736442261, 116343242472501442261, 20325073566675147442261, 3327107422474572347442261
Offset: 1

Views

Author

Seiichi Manyama, Apr 24 2022

Keywords

Crossrefs

Programs

  • Ruby
    def A(k, n)
      (1..n).map{|i| (1..i).to_a.reverse.join.to_i.to_s(k).to_i}
    end
    p A(8, 20)

Formula

a(n) = A007094(A000422(n)).

A004053 For m=2,3,..., write m in bases 2,3,..,m.

Original entry on oeis.org

10, 11, 10, 100, 11, 10, 101, 12, 11, 10, 110, 20, 12, 11, 10, 111, 21, 13, 12, 11, 10, 1000, 22, 20, 13, 12, 11, 10, 1001, 100, 21, 14, 13, 12, 11, 10, 1010, 101, 22, 20, 14, 13, 12, 11, 10, 1011, 102, 23, 21, 15, 14, 13, 12, 11, 10, 1100, 110, 30, 22, 20, 15, 14, 13, 12, 11, 10
Offset: 2

Views

Author

Johan Boye (johbo(AT)ida.liu.se)

Keywords

Examples

			Triangle begins:
    10;
    11,  10;
   100,  11, 10;
   101,  12, 11, 10;
   110,  20, 12, 11, 10;
   111,  21, 13, 12, 11, 10;
  1000,  22, 20, 13, 12, 11, 10;
  1001, 100, 21, 14, 13, 12, 11, 10;
  ...
		

Crossrefs

Programs

  • Mathematica
    FromDigits/@Flatten[Table[IntegerDigits[m,b],{m,2,20},{b,2,m}],1] (* Harvey P. Dale, Dec 01 2024 *)
  • PARI
    T(n, k) = fromdigits(digits(n, k), 10);
    tabl(nn) = for (n=2, nn, for (b=2, n, print1(T(n, b), ", "))); \\ Michel Marcus, Aug 30 2019

A037390 Numbers k such that every base-4 digit of k is a base-8 digit of k.

Original entry on oeis.org

1, 2, 3, 10, 42, 64, 65, 66, 67, 68, 69, 80, 85, 86, 90, 93, 95, 106, 128, 129, 130, 131, 136, 153, 160, 168, 169, 170, 171, 187, 192, 193, 194, 195, 234, 240, 250, 255, 257, 321, 514, 522, 528, 529, 530, 531, 532, 533, 534, 538
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Haskell
    import Data.List ((\\), nub)
    a037390 n = a037390_list !! (n-1)
    a037390_list = filter f [1..] where
       f x = null $ nub (ds 4 x) \\ nub (ds 8 x)
       ds b x = if x > 0 then d : ds b x' else []  where (x', d) = divMod x b
    -- Reinhard Zumkeller, May 30 2013

A037395 Numbers k such that every base-5 digit of k is a base-8 digit of k.

Original entry on oeis.org

1, 2, 3, 4, 83, 91, 93, 99, 124, 136, 161, 200, 206, 272, 314, 467, 524, 532, 540, 545, 546, 549, 609, 643, 656, 672, 680, 705, 706, 708, 770, 771, 774, 775, 776, 781, 784, 786, 787, 789, 793, 794, 796, 798, 799, 843, 871, 906
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Haskell
    import Data.List ((\\), nub)
    a037395 n = a037395_list !! (n-1)
    a037395_list = filter f [1..] where
       f x = null $ nub (ds 5 x) \\ nub (ds 8 x)
       ds b x = if x > 0 then d : ds b x' else []  where (x', d) = divMod x b
    -- Reinhard Zumkeller, May 30 2013
  • Mathematica
    Select[Range[1000],SubsetQ[IntegerDigits[#,8],IntegerDigits[#,5]]&] (* Harvey P. Dale, Oct 13 2015 *)

A063432 Triangle read by rows in which k-th entry in row n is representation of n in base k, for 1 <= k <= n.

Original entry on oeis.org

1, 11, 10, 111, 11, 10, 1111, 100, 11, 10, 11111, 101, 12, 11, 10, 111111, 110, 20, 12, 11, 10, 1111111, 111, 21, 13, 12, 11, 10, 11111111, 1000, 22, 20, 13, 12, 11, 10, 111111111, 1001, 100, 21, 14, 13, 12, 11, 10, 1111111111, 1010, 101, 22, 20, 14, 13
Offset: 1

Views

Author

Henry Bottomley, Jul 20 2001

Keywords

Comments

Representation of n in base 1 is defined to be a concatenation of n 1's.
It is difficult to write twenty-one in base 11 using decimal digits.
Representation in bases greater than 10 are written in base 10. This is really nasty! - N. J. A. Sloane, Dec 06 2002

Examples

			Rows start (1), (11, 10), (111, 11, 10), (1111, 100, 11, 10), etc.
		

Crossrefs

Cf. A063431.
Columns are truncated versions of A000042, A007088, A007089, A007090, A007091, A007092, A007093, A007094, A007095, A000027 and perhaps A055649, etc.
Without the 1st column becomes A004053.

Programs

  • Mathematica
    f[n_] := Flatten[ Append[ {FromDigits[ Table[1, {n}]] }, Table[ FromDigits[ IntegerDigits[n, i]], {i, 2, n}]]]; Flatten[ Table[ f[n], {n, 1, 10}]] (* Robert G. Wilson v *)

A102681 Number of digits >= 8 in decimal representation of n.

Original entry on oeis.org

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

Views

Author

N. J. A. Sloane, Feb 03 2005

Keywords

Comments

a(n) = 0 iff n is in A007094 (numbers in base 8). - Bernard Schott, Feb 18 2023

Crossrefs

Programs

  • Maple
    p:=proc(n) local b,ct,j: b:=convert(n,base,10): ct:=0: for j from 1 to nops(b) do if b[j]>=8 then ct:=ct+1 else ct:=ct fi od: ct: end: seq(p(n),n=0..120); # Emeric Deutsch, Feb 23 2005

Formula

From Hieronymus Fischer, Jun 10 2012: (Start)
a(n) = Sum_{j=1..m+1} (floor(n/10^j + 1/5) - floor(n/10^j)), where m = floor(log_10(n)).
G.f.: g(x) = (1/(1-x))*Sum_{j>=0} (x^(8*10^j) - x^(10*10^j))/(1 - x^10^(j+1)). (End)

Extensions

More terms from Emeric Deutsch, Feb 23 2005

A110606 Numbers n whose base 8 representations, interpreted as base 10 integers, are semiprimes.

Original entry on oeis.org

4, 6, 8, 12, 13, 17, 18, 21, 22, 27, 28, 29, 38, 41, 45, 47, 50, 53, 60, 63, 70, 73, 77, 81, 82, 83, 91, 92, 97, 98, 99, 101, 102, 109, 113, 118, 127, 129, 130, 131, 133, 134, 139, 140, 141, 143, 145, 150, 157, 159, 167, 171, 172, 178, 181, 183, 188, 193, 194, 195
Offset: 1

Views

Author

Jonathan Vos Post, Jul 30 2005

Keywords

Comments

A108873 is the equivalent using base 3. A110602 is the equivalent using base 4. A110603 is the equivalent using base 5. A110604 is the equivalent using base 6. A110605 is the equivalent using base 7. A110607 is the equivalent using base 9.

Examples

			a(1) = 4 because 4 (base 8) = 4 (base 10) = 2 * 2, a semiprime (A001358).
a(2) = 6 because 6 (base 8) = 6 (base 10) = 2 * 3.
a(3) = 8 because 8 (base 8) = 10 and 10 (base 10) = 2 * 5.
a(4) = 12 because 12 (base 8) = 14 and 14 (base 10) = 2 * 7.
a(5) = 13 because 13 (base 8) = 15 and 15 (base 10) = 3 * 5.
		

Crossrefs

Programs

  • Mathematica
    Select[Range[195], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 8]]] == 2 &] (* Ray Chandler, Aug 05 2005 *)

Extensions

Extended by Ray Chandler, Aug 05 2005

A353147 Decimal repunits written in base 8.

Original entry on oeis.org

0, 1, 13, 157, 2127, 25547, 331007, 4172107, 52305307, 647665707, 10216432707, 122621414707, 1473657200707, 20126330410707, 241540165130707, 3120702223570707, 37450626705270707, 473627744665470707, 6125757360430070707, 75533532545361070707
Offset: 0

Views

Author

Seiichi Manyama, Apr 26 2022

Keywords

Crossrefs

Programs

  • PARI
    a(n) = fromdigits(digits((10^n-1)/9, 8));
    
  • Python
    def a(n): return 0 if n == 0 else int(oct(int("1"*n))[2:])
    print([a(n) for n in range(13)]) # Michael S. Branicky, Apr 26 2022

Formula

a(n) = A007094(A002275(n)).

A000433 n written in base where place values are positive cubes.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22, 23, 24, 25, 26, 27, 30, 31, 32, 100, 101, 102, 103, 104, 105, 106, 107, 110, 111, 112, 113, 114, 115, 116, 117, 120, 121, 122, 123, 124, 125, 126, 127, 130, 131, 132, 200, 201, 202, 203
Offset: 0

Views

Author

R. Muller

Keywords

Comments

Let [d1, d2, d3, ...] be the decimal expansion of the n-th term, then dk is the number of times that the greedy algorithm subtracts the cube k^3 with input n. - Joerg Arndt, Nov 21 2014
For n > 1: A048766(n) = number of digits of a(n); A190311(n) = number of nonzero digits of a(n); A055401(n) = sum of digits of a(n). - Reinhard Zumkeller, May 08 2011
First differs from numbers written in base 8 (A007094) at a(27) = 100, whereas A007094(27) = 33. - Alonso del Arte, Nov 27 2014
The rightmost (least significant) digit never exceeds 7, the second digit from the right never exceeds 3, the third digit never exceeds 2, and the rest are just 0's and 1's. - Ivan Neretin, Sep 03 2015

Examples

			a(26) = 32 because 26 = 3 * 2^3 + 2 * 1^3.
a(27) = 100 because 27 = 3^3 + 0 * 2^3 + 0 * 1^3.
a(28) = 101 because 28 = 3^3 + 0 * 2^3 + 1 * 1^3.
		

References

  • Florentin Smarandache, "Properties of the Numbers", University of Craiova Archives, 1975; Arizona State University Special Collections, Tempe, AZ.

Crossrefs

Programs

  • Haskell
    import Data.Char (intToDigit)
    a000433 0 = 0
    a000433 n = read $ map intToDigit $
      t n $ reverse $ takeWhile (<= n) $ tail a000578_list where
          t _ []          = []
          t m (x:xs)
              | x > m     = 0 : t m xs
              | otherwise = (fromInteger m') : t r xs where (m',r) = divMod m x
    -- Reinhard Zumkeller, May 08 2011

A036285 Sequence A036284 written in octal.

Original entry on oeis.org

6, 30, 2640, 25664300, 2503026643656400, 25315703023056664357316564563000, 2527515731736303020414563050266643413731571505656462723056364000, 25246137277231573150136315064303020122720413505630571426364566664342075141145731573675057360256564674414627536305631724050230000
Offset: 0

Views

Author

Antti Karttunen, Nov 01 1998

Keywords

Crossrefs

Formula

a(n) = A007094(A036284(n)).

Extensions

Entry revised Dec 29 2007
Previous Showing 21-30 of 239 results. Next