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.

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A230856 Numbers n such that m + (sum of digits in base-3 representation of m) = n has exactly four solutions.

Original entry on oeis.org

248, 492, 978, 1222, 1708, 1952, 2192, 2196, 2436, 2680, 3166, 3410, 3896, 4140, 4380, 4384, 4624, 4868, 5354, 5598, 6084, 6328, 6566, 6572, 6810, 7054, 7540, 7784, 8270, 8514, 8754, 8758, 8998, 9242, 9728, 9972, 10458, 10702, 10942, 10946, 11186, 11430, 11916, 12160, 12646, 12890, 13128
Offset: 1

Views

Author

N. J. A. Sloane, Oct 31 2013

Keywords

Crossrefs

Related base-3 sequences: A053735, A134451, A230641, A230642, A230643, A230853, A230854, A230855, A230856, A230639, A230640, A010063 (trajectory of 1)

A290093 Compound filter (for base-3 digit runlengths): a(n) = P(A290091(n), A290092(n)), where P(n,k) is sequence A000027 used as a pairing function.

Original entry on oeis.org

1, 3, 2, 3, 10, 5, 2, 5, 7, 3, 21, 5, 10, 36, 14, 5, 27, 12, 2, 5, 16, 5, 14, 23, 7, 12, 29, 3, 21, 5, 21, 78, 27, 5, 27, 12, 10, 78, 14, 36, 136, 44, 14, 90, 25, 5, 27, 23, 27, 90, 61, 12, 42, 38, 2, 5, 16, 5, 14, 23, 16, 23, 67, 5, 27, 23, 14, 44, 40, 23, 61, 80, 7, 12, 67, 12, 25, 80, 29, 38, 121, 3, 21, 5, 21, 78, 27, 5, 27, 12, 21, 465, 27, 78, 300, 90, 27
Offset: 0

Views

Author

Antti Karttunen, Jul 25 2017

Keywords

Comments

For all i, j: a(i) = a(j) => A006047(i) = A006047(j) => A053735(i) = A053735(j).

Crossrefs

Cf. A006047, A053735, A290079 (some of the matched sequences).

Programs

Formula

a(n) = (1/2)*(2 + ((A290091(n)+A290092(n))^2) - A290091(n) - 3*A290092(n)).

A033095 Number of 1's when n is written in base b for 2<=b<=n+1.

Original entry on oeis.org

1, 1, 3, 4, 6, 6, 9, 6, 10, 10, 12, 11, 16, 13, 15, 14, 16, 13, 18, 15, 21, 20, 21, 16, 24, 20, 23, 23, 26, 25, 32, 22, 26, 25, 25, 28, 34, 28, 32, 30, 35, 30, 37, 31, 35, 36, 35, 31, 41, 34, 37, 36, 39, 35, 43, 38, 44, 41, 42, 38, 49, 40, 43
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_] := Count[Flatten@ Table[ IntegerDigits[n, b], {b, 2, n + 1}], 1]; Array[f, 63] (* Robert G. Wilson v, Nov 14 2012 *)

Formula

G.f.: x+(Sum_{b>=2} (Sum_{k>=0} x^(b^k)/(Sum_{0<=iFranklin T. Adams-Watters, Nov 03 2005

A053831 Sum of digits of n written in base 11.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15
Offset: 0

Views

Author

Henry Bottomley, Mar 28 2000

Keywords

Comments

Also the fixed point of the morphism 0->{0,1,2,3,4,5,6,7,8,9,10}, 1->{1,2,3,4,5,6,7,8,9,10,11}, 2->{2,3,4,5,6,7,8,9,10,11,12}, etc. - Robert G. Wilson v, Jul 27 2006

Examples

			a(20) = 1 + 9 = 10 because 20 is written as 19 base 11.
		

Crossrefs

Sum of digits of n written in bases 2-16: A000120, A053735, A053737, A053824, A053827, A053828, A053829, A053830, A007953, this sequence, A053832, A053833, A053834, A053835, A053836.

Programs

  • C
    int Base11DigitSum(int n) {
       int count = 0;
       while (n != 0) { count += n % 11; n = n / 11; }
       return count;
    } // Tanar Ulric, Oct 20 2021
  • Mathematica
    Table[Plus @@ IntegerDigits[n, 11], {n, 0, 86}] (* or *)
    Nest[ Flatten[ #1 /. a_Integer -> Table[a + i, {i, 0, 10}]] &, {0}, 2] (* Robert G. Wilson v, Jul 27 2006 *)
  • PARI
    a(n)=if(n<1,0,if(n%11,a(n-1)+1,a(n/11)))
    
  • PARI
    a(n)=sumdigits(n,11) \\ Charles R Greathouse IV, Oct 20 2021
    

Formula

From Benoit Cloitre, Dec 19 2002: (Start)
a(0)=0, a(11n+i) = a(n)+i for 0 <= i <= 10.
a(n) = n-(m-1)*(Sum_{k>0} floor(n/m^k)) = n-(m-1)*A064458(n). (End)
a(n) = A138530(n,11) for n > 10. - Reinhard Zumkeller, Mar 26 2008
Sum_{n>=1} a(n)/(n*(n+1)) = 11*log(11)/10 (Shallit, 1984). - Amiram Eldar, Jun 03 2021

A173525 a(n) = 1 + A053824(n-1), where A053824 = sum of digits in base 5.

Original entry on oeis.org

1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 7, 8, 9, 10, 11, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 7, 8, 9, 10, 11, 8, 9, 10, 11, 12
Offset: 1

Views

Author

Omar E. Pol, Feb 20 2010

Keywords

Comments

Also: a(n) = A053824(5^k+n-1) in the limit k->infinity, where k plays the role of a row index in A053824. (See the comment by M. F. Hasler for the proof.)
This means: if A053824 is regarded as a triangle then the rows converge to this sequence.
See conjecture in the entry A000120, and the case of base 2 in A063787.
From R. J. Mathar, Dec 09 2010: (Start)
In base b=5, A053824 starts counting up from 1 each time the index wraps around a power of b: A053824(b^k)=1.
Obvious recurrences are A053824(m*b^k+i) = m+A053824(i), 1 <= m < b-1, 0 <= i < b^(k-1).
So A053824 can be decomposed into a triangle T(k,n) = A053824(b^k+n-1), assuming that column indices start at n=1; row lengths are (b-1)*b^k.
There is a self-similarity in these sequences; a sawtooth structure of periodicity b is added algebraically on top of a sawtooth structure of periodicity b^2, on top of a periodicity b^3 etc. This leads to some "fake" finitely periodic substructures in the early parts of each row of T(.,.): often, but not always, a(n+b)=1+a(n). Often, but not always, a(n+b^2)=1+a(n) etc.
The common part of the rows T(.,.) grows with the power of b as shown in the recurrence above, and defines a(n) in the limit of large row indices k. (End)
The two definitions agree because the first 5^r terms in each row correspond to numbers 5^r, 5^r+1,...,5^r+(5^r-1), which are written in base 5 as a leading 1 plus the digits of 0,...,5^r-1. - M. F. Hasler, Dec 09 2010
From Omar E. Pol, Dec 10 2010: (Start)
In the scatter plots of these sequences, the basic structure is an element with b^2 points, where b is the associated base. (Scatter plots are created with the "graph" button of a sequence.) Sketches of these structures look as follows, the horizontal axis a squeezed version of the index n, b consecutive points packed vertically, and the vertical axis a(n):
........................................................
................................................ * .....
............................................... ** .....
..................................... * ...... *** .....
.................................... ** ..... **** .....
.......................... * ...... *** .... ***** .....
......................... ** ..... **** ... ****** .....
............... * ...... *** .... ***** ... ***** ......
.............. ** ..... **** .... **** .... **** .......
.... * ...... *** ..... *** ..... *** ..... *** ........
... ** ...... ** ...... ** ...... ** ...... ** .........
... * ....... * ....... * ....... * ....... * ..........
........................................................
... b=2 ..... b=3 ..... b=4 ..... b=5 ..... b=6 ........
........................................................
............................................. * ........
............................................ ** ........
........................... * ............. *** ........
.......................... ** ............ **** ........
........... *............ *** ........... ***** ........
.......... ** .......... **** .......... ****** ........
......... ***.......... ***** ......... ******* ........
........ **** ........ ****** ........ ******** ........
....... ***** ....... ******* ....... ********* ........
...... ****** ...... ******** ....... ******** .........
..... ******* ...... ******* ........ ******* ..........
..... ****** ....... ****** ......... ****** ...........
..... ***** ........ ***** .......... ***** ............
..... **** ......... **** ........... **** .............
..... *** .......... *** ............ *** ..............
..... ** ........... ** ............. ** ...............
..... * ............ * .............. * ................
........................................................
..... b=7 .......... b=8 ............ b=9 ..............
... A053828 ...... A053829 ........ A053830 ............
... A173527 ...... A173528 ........ A173529 ............(End)

Crossrefs

Programs

  • Haskell
    a173525 = (+ 1) . a053824 . (subtract 1) -- Reinhard Zumkeller, Jan 31 2014
  • Maple
    A053825 := proc(n) add(d, d=convert(n,base,5)) ; end proc:
    A173525 := proc(n) local b,k; b := 5 ; if n < b then n; else k := n/(b-1);   k := ceil(log(k)/log(b)) ; A053825(b^k+n-1) ; end if; end proc:
    seq(A173525(n),n=1..100) ;
  • Mathematica
    Total[IntegerDigits[#,5]]+1&/@Range[0,100] (* Harvey P. Dale, Jun 14 2015 *)
  • PARI
    A173525(n)={ my(s=1); n--; until(!n\=5, s+=n%5); s } \\ M. F. Hasler, Dec 09 2010
    
  • PARI
    A173525(n)={ my(s=1+(n=divrem(n-1,5))[2]); while((n=divrem(n[1],5))[1],s+=n[2]); s+n[2] } \\ M. F. Hasler, Dec 09 2010
    

Formula

a(n) = A053824(5^k + n - 1) where k >= ceiling(log_5(n/4)). - R. J. Mathar, Dec 09 2010

Extensions

More terms from Vincenzo Librandi, Aug 02 2010

A240236 Triangle read by rows: sum of digits of n in base k, for 2<=k<=n.

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			Triangle starts:
  1
  2 1
  1 2 1
  2 3 2 1
  2 2 3 2 1
  3 3 4 3 2 1
		

Crossrefs

Row sums give A043306.
See A138530 for another version.

Programs

  • Haskell
    a240236 n k = a240236_tabl !! (n-1) !! (k-1)
    a240236_row n = a240236_tabl !! (n-1)
    a240236_tabl = zipWith (map . flip q)
                           [2..] (map tail $ tail a002260_tabl) where
       q b n = if n < b then n else q b n' + d where (n', d) = divMod n b
    -- Reinhard Zumkeller, Apr 29 2015
  • Mathematica
    Table[Total[Flatten[IntegerDigits[n,k]]],{n,20},{k,2,n}]//Flatten (* Harvey P. Dale, Jan 13 2025 *)
  • PARI
    T(n,k) = local(r=0);if(k<2,-1,while(n>0,r+=n%k;n\=k);r)
    
  • PARI
    T(n, k) = sumdigits(n, k) \\ Zhuorui He, Aug 25 2025
    

Formula

T(n,k) = n - (k - 1) * Sum_{i=1..floor(log_k(n))} floor(n/k^i). - Ridouane Oudra, Sep 27 2024
T(n,k) = n - (k - 1) * A090623(n,k). - Zhuorui He, Aug 25 2025

A290094 Restricted growth sequence transform of A290093.

Original entry on oeis.org

1, 2, 3, 2, 4, 5, 3, 5, 6, 2, 7, 5, 4, 8, 9, 5, 10, 11, 3, 5, 12, 5, 9, 13, 6, 11, 14, 2, 7, 5, 7, 15, 10, 5, 10, 11, 4, 15, 9, 8, 16, 17, 9, 18, 19, 5, 10, 13, 10, 18, 20, 11, 21, 22, 3, 5, 12, 5, 9, 13, 12, 13, 23, 5, 10, 13, 9, 17, 24, 13, 20, 25, 6, 11, 23, 11, 19, 25, 14, 22, 26, 2, 7, 5, 7, 15, 10, 5, 10, 11, 7, 27, 10, 15, 28, 18, 10, 29, 21, 5, 10, 13
Offset: 0

Views

Author

Antti Karttunen, Jul 26 2017

Keywords

Crossrefs

For all i, j: a(i) = a(j) <=> A290093(n) = A290093(n), thus this matches to all the same base-3 (ternary) related sequences as A290093: A006047, A053735, A062756, A081603, A117942, A206424, A227428, A290091, A290092, A290079, and many others.

A000989 3-adic valuation of binomial(2*n, n): largest k such that 3^k divides binomial(2*n, n).

Original entry on oeis.org

0, 0, 1, 0, 0, 2, 1, 1, 2, 0, 0, 1, 0, 0, 3, 2, 2, 3, 1, 1, 2, 1, 1, 3, 2, 2, 3, 0, 0, 1, 0, 0, 2, 1, 1, 2, 0, 0, 1, 0, 0, 4, 3, 3, 4, 2, 2, 3, 2, 2, 4, 3, 3, 4, 1, 1, 2, 1, 1, 3, 2, 2, 3, 1, 1, 2, 1, 1, 4, 3, 3, 4, 2, 2, 3, 2, 2, 4, 3, 3
Offset: 0

Views

Author

Keywords

Comments

a(n) = 0 if and only if n is in A005836. - Charles R Greathouse IV, May 19 2013
sign(a(n+1) - a(n)) is repeat [0, 1, -1]. - Filip Zaludek, Oct 29 2016
By Kummer's theorem, number of carries when adding n + n in base 3. - Robert Israel, Oct 30 2016

Crossrefs

Programs

  • Haskell
    a000989 = a007949 . a000984  -- Reinhard Zumkeller, Nov 19 2015
  • Maple
    f:= proc(n) option remember; local k,m,d;
       k:= floor(log[3](n));
       d:= floor(n/3^k);
       m:= n-d*3^k;
       if d = 2 or 2*m > 3^k then procname(m)+1
       else procname(m)
       fi
    end proc:
    f(0):= 0:
    map(f, [$0..100]); # Robert Israel, Oct 30 2016
  • Mathematica
    p=3; Array[ If[ Mod[ bi=Binomial[ 2#, # ], p ]==0, Select[ FactorInteger[ bi ], Function[ q, q[ [ 1 ] ]==p ], 1 ][ [ 1, 2 ] ], 0 ]&, 27*3, 0 ]
    Table[ IntegerExponent[ Binomial[2 n, n], 3], {n, 0, 100}] (* Jean-François Alcover, Feb 15 2016 *)
  • PARI
    a(n) = valuation(binomial(2*n, n), 3)
    
  • PARI
    a(n)=my(N=2*n,s);while(N\=3,s+=N);while(n\=3,s-=2*n);s \\ Charles R Greathouse IV, May 19 2013
    

Formula

a(n) = Sum_{k>=0} floor(2*n/3^k) - 2*Sum_{k>=0} floor(n/3^k). - Benoit Cloitre, Aug 26 2003
a(n) = A007949(A000984(n)). - Reinhard Zumkeller, Nov 19 2015
From Robert Israel, Oct 30 2016: (Start)
If 2*n < 3^k then a(3^k+n) = a(n).
If n < 3^k < 2*n then a(3^k+n) = a(n)+1.
If n < 3^k then a(2*3^k+n) = a(n)+1. (End)
a(n) = A053735(n) - A053735(2*n)/2. - Amiram Eldar, Feb 12 2021
From Miles Wilson, Jul 06 2025: (Start)
a(n) = A007949(n+1) + A067397(n).
G.f.: Sum_{k>=1} (x^(3^k/2+1/2)-x^(3^k))/((x-1)*(x^(3^k)-1)). (End)

A006287 Sum of squares of digits of ternary representation of n.

Original entry on oeis.org

0, 1, 4, 1, 2, 5, 4, 5, 8, 1, 2, 5, 2, 3, 6, 5, 6, 9, 4, 5, 8, 5, 6, 9, 8, 9, 12, 1, 2, 5, 2, 3, 6, 5, 6, 9, 2, 3, 6, 3, 4, 7, 6, 7, 10, 5, 6, 9, 6, 7, 10, 9, 10, 13, 4, 5, 8, 5, 6, 9, 8, 9, 12, 5, 6, 9, 6, 7
Offset: 0

Views

Author

Keywords

References

  • Jeffrey Shallit, personal communication.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Maple
    A006287 := proc(n)
        local d ;
        convert(n,base,3) ;
        add(d^2,d=%) ;
    end proc: # R. J. Mathar, Jun 13 2014
  • Mathematica
    Table[Total[IntegerDigits[n,3]^2],{n,0,80}]  (* Harvey P. Dale, Apr 23 2011 *)

A239619 Base 3 sum of digits of prime(n).

Original entry on oeis.org

2, 1, 3, 3, 3, 3, 5, 3, 5, 3, 3, 3, 5, 5, 5, 7, 5, 5, 5, 7, 5, 7, 3, 5, 5, 5, 5, 7, 3, 5, 5, 7, 5, 5, 7, 7, 7, 3, 5, 5, 7, 5, 5, 5, 7, 5, 7, 7, 7, 7, 9, 9, 9, 5, 5, 5, 7, 3, 5, 5, 5, 7, 5, 7, 7, 7, 5, 5, 7, 7, 5, 7, 7, 7, 5, 7, 7, 7, 9, 5, 7, 7, 9, 5, 7, 7, 9
Offset: 1

Views

Author

Tom Edgar, Mar 22 2014

Keywords

Examples

			The fifth prime is 11, 11 in base 3 is (1,0,2) so a(5)=1+0+2=3.
		

Crossrefs

Programs

  • Magma
    [&+Intseq(NthPrime(n),3): n in [1..100]]; // Vincenzo Librandi, Mar 25 2014
    
  • Mathematica
    Table[Plus @@ IntegerDigits[Prime[n], 3], {n, 1, 100}] (* Vincenzo Librandi, Mar 25 2014 *)
  • PARI
    a(n) = vecsum(digits(prime(n), 3)); \\ Michel Marcus, Mar 07 2020
  • Sage
    [sum(i.digits(base=3)) for i in primes_first_n(200)]
    

Formula

a(n) = A053735(A000040(n)).
Previous Showing 51-60 of 117 results. Next