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 11-19 of 19 results.

A033048 Sums of distinct powers of 12.

Original entry on oeis.org

0, 1, 12, 13, 144, 145, 156, 157, 1728, 1729, 1740, 1741, 1872, 1873, 1884, 1885, 20736, 20737, 20748, 20749, 20880, 20881, 20892, 20893, 22464, 22465, 22476, 22477, 22608, 22609, 22620, 22621, 248832, 248833, 248844, 248845, 248976
Offset: 0

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Author

Keywords

Comments

Numbers without any base-12 digits greater than 1.

Crossrefs

Subsequence of A102487.
Row 11 of array A104257.

Programs

  • Haskell
    import Data.List (unfoldr)
    a033048 n = a033048_list !! (n-1)
    a033048_list = filter (all (< 2) . unfoldr (\x ->
       if x == 0 then Nothing else Just $ swap $ divMod x 12)) [1..]
    -- Reinhard Zumkeller, Apr 17 2011
  • Mathematica
    With[{k = 12}, Map[FromDigits[#, k] &, Tuples[{0, 1}, 6]]] (* Michael De Vlieger, Oct 28 2022 *)
  • PARI
    {maxn=37;
    for(vv=0,maxn,
    bvv=binary(vv);
    ll=length(bvv);texp=0;btod=0;
    forstep(i=ll,1,-1,btod=btod+bvv[i]*12^texp;texp++);
    print1(btod,", "))}
    \\ Douglas Latimer, Apr 16 2012
    
  • PARI
    a(n)=fromdigits(binary(n),12) \\ Charles R Greathouse IV, Jan 11 2017
    

Formula

a(n) = Sum_{i=0..m} d(i)*12^i, where Sum_{i=0..m} d(i)*2^i is the base-2 representation of n.
a(n) = A097258(n)/11.
a(2n) = 12*a(n), a(2n+1) = a(2n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*b(k) with b(k) = 12^k = A001021(k). - Philippe Deléham, Oct 19 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 12^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Extended by Ray Chandler, Aug 03 2004

A115845 Numbers n such that there is no bit position where the binary expansions of n and 8n are both 1.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 17, 20, 21, 24, 28, 32, 33, 34, 35, 40, 42, 48, 49, 56, 64, 65, 66, 67, 68, 69, 70, 71, 80, 81, 84, 85, 96, 97, 98, 99, 112, 113, 128, 129, 130, 131, 132, 133, 134, 135, 136, 138, 140, 142, 160, 161, 162, 163, 168, 170, 192
Offset: 1

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Author

Antti Karttunen, Feb 01 2006

Keywords

Comments

Equivalently, numbers n such that 9*n = 9 X n, i.e., 8*n XOR n = 9*n. Here * stands for ordinary multiplication and X means carryless (GF(2)[X]) multiplication (A048720).
Equivalently, numbers n such that the binomial coefficient C(9n,n) (A169958) is odd. - Zak Seidov, Aug 06 2010
The equivalence of these three definitions follows from Lucas's theorem on binomial coefficients. - N. J. A. Sloane, Sep 01 2010
Clearly all numbers k*2^i for 1 <= k <= 7 have this property. - N. J. A. Sloane, Sep 01 2010
A116361(a(n)) <= 3. - Reinhard Zumkeller, Feb 04 2006

Crossrefs

A115846 shows this sequence in binary.
A033052 is a subsequence.

Programs

  • Mathematica
    Reap[Do[If[OddQ[Binomial[9n,n]],Sow[n]],{n,0,400}]][[2,1]] (* Zak Seidov, Aug 06 2010 *)
  • PARI
    is(n)=!bitand(n,n<<3) \\ Charles R Greathouse IV, Sep 23 2012

Formula

a(n)/n^k is bounded (but does not tend to a limit), where k = 1.44... = A104287. - Charles R Greathouse IV, Sep 23 2012

Extensions

Edited with a new definition by N. J. A. Sloane, Sep 01 2010, merging this sequence with a sequence submitted by Zak Seidov, Aug 06 2010

A033047 Sums of distinct powers of 11.

Original entry on oeis.org

0, 1, 11, 12, 121, 122, 132, 133, 1331, 1332, 1342, 1343, 1452, 1453, 1463, 1464, 14641, 14642, 14652, 14653, 14762, 14763, 14773, 14774, 15972, 15973, 15983, 15984, 16093, 16094, 16104, 16105, 161051, 161052, 161062, 161063, 161172
Offset: 0

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Author

Keywords

Comments

Numbers without any base-11 digits greater than 1.
a(n) modulo 2 is the Prouhet-Thue-Morse sequence A010060. - Philippe Deléham, Oct 17 2011

Crossrefs

Row 10 of array A104257.

Programs

  • Mathematica
    With[{k = 11}, Map[FromDigits[#, k] &, Tuples[{0, 1}, 6]]] (* Michael De Vlieger, Oct 28 2022 *)
  • PARI
    {for(vv=0,35,
    bvv=binary(vv);
    texp=0;btb=0;
    forstep(i=length(bvv),1,-1,btb=btb+bvv[i]*11^texp;texp++);
    print1(btb,", "))} \\ Douglas Latimer, May 12 2012
    
  • PARI
    a(n)=fromdigits(binary(n),11) \\ Charles R Greathouse IV, Jan 11 2017

Formula

a(n) = Sum_{i=0..m} d(i)*11^i, where Sum_{i=0..m} d(i)*2^i is the base-2 representation of n.
a(n) = A097257(n)/10.
a(2n) = 11*a(n), a(2n+1) = a(2n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*11^k. - Philippe Deléham, Oct 17 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 11^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Extended by Ray Chandler, Aug 03 2004

A033049 Sums of distinct powers of 13.

Original entry on oeis.org

0, 1, 13, 14, 169, 170, 182, 183, 2197, 2198, 2210, 2211, 2366, 2367, 2379, 2380, 28561, 28562, 28574, 28575, 28730, 28731, 28743, 28744, 30758, 30759, 30771, 30772, 30927, 30928, 30940, 30941, 371293, 371294, 371306, 371307, 371462
Offset: 0

Views

Author

Keywords

Comments

Numbers without any base-13 digits greater than 1.
a(n) modulo 2 is the Prouhet-Thue-Morse sequence A010060. - Philippe Deléham, Oct 17 2011

Crossrefs

Row 12 of array A104257.

Programs

  • Mathematica
    With[{k = 13}, Map[FromDigits[#, k] &, Tuples[{0, 1}, 6]]] (* Michael De Vlieger, Oct 28 2022 *)
  • PARI
    A033049(n,b=13)=subst(Pol(binary(n)),'x,b) \\ M. F. Hasler, Feb 01 2016

Formula

a(n) = Sum_{i=0..m} d(i)*13^i, where Sum_{i=0..m} d(i)*2^i is the base-2 representation of n.
a(n) = A097259(n)/12.
a(2n) = 13*a(n), a(2n+1) = a(2n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*13^k. - Philippe Deléham, Oct 17 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 13^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Extended by Ray Chandler, Aug 03 2004

A033051 Numbers whose set of base 15 digits is {0,1}.

Original entry on oeis.org

0, 1, 15, 16, 225, 226, 240, 241, 3375, 3376, 3390, 3391, 3600, 3601, 3615, 3616, 50625, 50626, 50640, 50641, 50850, 50851, 50865, 50866, 54000, 54001, 54015, 54016, 54225, 54226, 54240, 54241, 759375, 759376, 759390, 759391, 759600
Offset: 0

Views

Author

Keywords

Comments

Sums of distinct powers of 15.
a(n) modulo 2 is the Prouhet-Thue-Morse sequence A010060. - Philippe Deléham, Oct 17 2011.

Crossrefs

Row 14 of array A104257.

Programs

  • Mathematica
    With[{k = 15}, Map[FromDigits[#, k] &, Tuples[{0, 1}, 6]]] (* Michael De Vlieger, Oct 28 2022 *)
    FromDigits[#,15]&/@Tuples[{0,1},6] (* Harvey P. Dale, Sep 15 2024 *)
  • PARI
    A033051(n, b=15)=subst(Pol(binary(n)),'x,b) \\ M. F. Hasler, Feb 01 2016

Formula

a(n) = Sum_{i=0..m} d(i)*15^i, where Sum_{i=0..m} d(i)*2^i is the base-2 representation of n.
a(n) = A097261(n)/14.
a(2n) = 15*a(n), a(2n+1) = a(2n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*15^k. - Philippe Deléham, Oct 17 2011.
G.f.: (1/(1 - x))*Sum_{k>=0} 15^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Extended by Ray Chandler, Aug 03 2004

A033050 Numbers whose set of base 14 digits is {0,1}.

Original entry on oeis.org

0, 1, 14, 15, 196, 197, 210, 211, 2744, 2745, 2758, 2759, 2940, 2941, 2954, 2955, 38416, 38417, 38430, 38431, 38612, 38613, 38626, 38627, 41160, 41161, 41174, 41175, 41356, 41357, 41370, 41371, 537824, 537825, 537838, 537839, 538020
Offset: 0

Views

Author

Keywords

Comments

Sums of distinct powers of 14.
The base-14 digits may comprise zero, one, or both. - Harvey P. Dale, May 12 2014

Crossrefs

Row 13 of array A104257.

Programs

  • Mathematica
    Select[Range[0,540000],Max[IntegerDigits[#,14]]<2&] (* Harvey P. Dale, May 12 2014 *)
    FromDigits[#,14]&/@Tuples[{0,1},6] (* Harvey P. Dale, Jun 18 2021 *)
  • PARI
    A033050(n,b=14)=subst(Pol(binary(n)),'x,b) \\ M. F. Hasler, Feb 01 2016

Formula

a(n) = Sum_{i=0..m} d(i)*14^i, where Sum_{i=0..m} d(i)*2^i is the base-2 representation of n.
a(n) = A097260(n)/13.
a(2n) = 14*a(n), a(2n+1) = a(2n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*14^k. - Philippe Deléham, Oct 20 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 14^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Extended by Ray Chandler, Aug 03 2004

A063012 Sum of distinct powers of 20; i.e., numbers with digits in {0,1} base 20; i.e., write n in base 2 and read as if written in base 20.

Original entry on oeis.org

0, 1, 20, 21, 400, 401, 420, 421, 8000, 8001, 8020, 8021, 8400, 8401, 8420, 8421, 160000, 160001, 160020, 160021, 160400, 160401, 160420, 160421, 168000, 168001, 168020, 168021, 168400, 168401, 168420, 168421, 3200000, 3200001, 3200020, 3200021, 3200400, 3200401
Offset: 0

Views

Author

Henry Bottomley, Jul 04 2001

Keywords

Examples

			a(5) = 401 since 5 written in base 2 is 101 so a(5) = 1*20^2 + 0*20^1 + 1*20^0 = 400 + 0 + 1 = 401.
		

Crossrefs

A063013 is similar in a different way.

Programs

  • Maple
    a:= proc(n) `if`(n<2, n, irem(n, 2, 'r')+20*a(r)) end:
    seq(a(n), n=0..37);  # Alois P. Heinz, Apr 04 2025
  • Mathematica
    Table[FromDigits[IntegerDigits[n,2],20],{n,0,40}] (* Harvey P. Dale, Jul 21 2014 *)
  • PARI
    baseE(x, b)= { local(d, e, f); e=0; f=1; while (x>0, d=x-b*(x\b); x\=b; e+=d*f; f*=10); return(e) }
    baseI(x, b)= { local(d, e, f); e=0; f=1; while (x>0, d=x-10*(x\10); x\=10; e+=d*f; f*=b); return(e) }
    { for (n=0, 1000, write("b063012.txt", n, " ", baseI(baseE(n, 2), 20)) ) } \\ Harry J. Smith, Aug 15 2009
    
  • Python
    def A063012(n): return int(bin(n)[2:],20) # Chai Wah Wu, Apr 04 2025

Formula

a(n) = a(n-2^floor(log_2(n))) + 20^floor(log_2(n)). a(2n) = 20*a(n); a(2n+1) = a(2n)+1 = 20*a(n)+1.
a(n) = Sum_{k>=0} A030308(n,k)*A009964(k). - Philippe Deléham, Oct 15 2011
G.f.: (1/(1 - x))*Sum_{k>=0} 20^k*x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Jun 04 2017

Extensions

Edited by Charles R Greathouse IV, Aug 02 2010

A351995 Square array A(n, k), n, k >= 0, read by antidiagonals upwards; A(n, k) = Sum_{ i >= 0 } b_i * 2^(k*i) where n = Sum_{ i >= 0 } b_i * 2^i.

Original entry on oeis.org

0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 1, 3, 4, 1, 0, 2, 4, 5, 8, 1, 0, 2, 5, 16, 9, 16, 1, 0, 3, 6, 17, 64, 17, 32, 1, 0, 1, 7, 20, 65, 256, 33, 64, 1, 0, 2, 8, 21, 72, 257, 1024, 65, 128, 1, 0, 2, 9, 64, 73, 272, 1025, 4096, 129, 256, 1, 0, 3, 10, 65, 512, 273, 1056, 4097, 16384, 257, 512, 1, 0
Offset: 0

Views

Author

Rémy Sigrist, Feb 27 2022

Keywords

Comments

In other words, in binary expansion of n, replace 2^i by 2^(k*i).

Examples

			Square array A(n, k) begins:
  n\k|  0  1   2   3    4     5     6      7      8       9       10
  ------------------------------------------------------------------
    0|  0  0   0   0    0     0     0      0      0       0        0
    1|  1  1   1   1    1     1     1      1      1       1        1
    2|  1  2   4   8   16    32    64    128    256     512     1024
    3|  2  3   5   9   17    33    65    129    257     513     1025
    4|  1  4  16  64  256  1024  4096  16384  65536  262144  1048576
    5|  2  5  17  65  257  1025  4097  16385  65537  262145  1048577
    6|  2  6  20  72  272  1056  4160  16512  65792  262656  1049600
    7|  3  7  21  73  273  1057  4161  16513  65793  262657  1049601
		

Crossrefs

Programs

  • Mathematica
    A351995[n_, k_] := If[n <= 1, n, Total[2^(k*(Flatten[Position[Reverse[IntegerDigits[n, 2]], 1]] - 1))]];
    Table[A351995[n - k, k], {n, 0, 15}, {k, 0, n}] (* Paolo Xausa, Aug 26 2025 *)
  • PARI
    A(n,k) = { my (v=0, e); while (n, n-=2^e=valuation(n, 2); v+=2^(k*e)); v }

Formula

A(A(n, k), k') = A(n, k*k') for k, k' > 0.
A(n, 0) = A000120(n).
A(n, 1) = n.
A(n, 2) = A000695(n).
A(n, 3) = A033045(n).
A(n, 4) = A033052(n).
A(0, k) = 0.
A(1, k) = 1.
A(2, k) = 2^k.
A(3, k) = 2^k + 1.

A147845 Odd positive integers a(n) such that for every odd integer m>=7 there exists a unique representation of the form m=a(p)+2a(q)+4a(r).

Original entry on oeis.org

1, 3, 17, 19, 129, 131, 145, 147, 1025, 1027, 1041, 1043, 1153, 1155, 1169, 1171, 8193, 8195, 8209, 8211, 8321, 8323, 8337, 8339, 9217, 9219, 9233, 9235, 9345, 9347, 9361, 9363, 65537, 65539, 65553, 65555
Offset: 1

Views

Author

Vladimir Shevelev, Nov 15 2008

Keywords

Comments

Since, e.g., 27=17+2*3+4*1 and 17=a(3),3=a(2),1=a(1), then 27 has "coordinates" (3,2,1). Thus we have a one-to-one map of odd integers >=7 to the positive lattice points in the three-dimensional space.

Crossrefs

Formula

a(n)=2A033045(n-1)+1
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