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 61-68 of 68 results.

A334603 Period of the fraction 1/11^n for n >= 1.

Original entry on oeis.org

2, 22, 242, 2662, 29282, 322102, 3543122, 38974342, 428717762, 4715895382, 51874849202, 570623341222, 6276856753442, 69045424287862, 759499667166482, 8354496338831302, 91899459727144322, 1010894056998587542, 11119834626984462962, 122318180896829092582
Offset: 1

Views

Author

Bernard Schott, May 07 2020

Keywords

Comments

Conjecture proposed by the authors in References page 205: if p is a prime with gcd(p,30) = 1 and if the period of 1/p is m then the period of 1/p^n is m*p^(n-1).

Examples

			1/121 = 0. 0082644628099173553719 0082644628099173553719 ... with periodic part {0082644628099173553719}, whose length is 22 digits, so a(2) = 22.
		

References

  • J.-M. De Koninck & A. Mercier, 1001 Problèmes en Théorie Classique des Nombres, Problème 346 pp. 50, 204-205, Ellipses, Paris 2004.

Crossrefs

Cf. period of fractions: A051626 (1/n), A133494 (1/3^n), A055272 (1/7^n).
Cf. A001020 (11^n).

Programs

  • Mathematica
    MultiplicativeOrder[10, 11^#] & /@ Range[20] (* Giovanni Resta, May 07 2020 *)
  • PARI
    a(n) = znorder(Mod(10, 11^n)); \\ Michel Marcus, May 09 2020

Formula

a(n) = 2 * 11^(n-1) [conjectured, see comments].
a(n) = A051626(A001020(n)).

Extensions

More terms from Giovanni Resta, May 07 2020

A358138 Difference between maximum and minimum part in the n-th composition in standard order.

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 0, 0, 2, 0, 1, 2, 1, 1, 0, 0, 3, 1, 2, 1, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 0, 0, 4, 2, 3, 0, 2, 2, 2, 2, 2, 0, 1, 2, 1, 1, 1, 4, 3, 2, 2, 2, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 0, 0, 5, 3, 4, 1, 3, 3, 3, 1, 2, 1, 2, 2, 2, 2, 2, 3, 3, 1, 2, 1, 1, 1, 1
Offset: 1

Views

Author

Gus Wiseman, Oct 31 2022

Keywords

Comments

The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.

Crossrefs

See link for sequences related to standard compositions.
The first and last parts are A065120 and A001511, difference A358135.
This is the maximum minus minimum part in row n of A066099.
The version for Heinz numbers of partitions is A243055.
The maximum and minimum parts are A333766 and A333768.
The partial sums of standard compositions are A358134, adjusted A242628.
A011782 counts compositions.
A351014 counts distinct runs in standard compositions.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    Table[Max[stc[n]]-Min[stc[n]],{n,1,100}]

Formula

a(n) = A333766(n) - A333768(n).

A359041 Number of finite sets of integer partitions with all equal sums and total sum n.

Original entry on oeis.org

1, 1, 2, 3, 6, 7, 14, 15, 32, 31, 63, 56, 142, 101, 240, 211, 467, 297, 985, 490, 1524, 1247, 2542, 1255, 6371, 1979, 7486, 7070, 14128, 4565, 32953, 6842, 42229, 37863, 56266, 17887, 192914, 21637, 145820, 197835, 371853, 44583, 772740, 63261, 943966, 1124840
Offset: 0

Views

Author

Gus Wiseman, Dec 14 2022

Keywords

Examples

			The a(1) = 1 through a(6) = 14 sets:
  {(1)}  {(2)}   {(3)}    {(4)}       {(5)}      {(6)}
         {(11)}  {(21)}   {(22)}      {(32)}     {(33)}
                 {(111)}  {(31)}      {(41)}     {(42)}
                          {(211)}     {(221)}    {(51)}
                          {(1111)}    {(311)}    {(222)}
                          {(2),(11)}  {(2111)}   {(321)}
                                      {(11111)}  {(411)}
                                                 {(2211)}
                                                 {(3111)}
                                                 {(21111)}
                                                 {(111111)}
                                                 {(3),(21)}
                                                 {(3),(111)}
                                                 {(21),(111)}
		

Crossrefs

This is the constant-sum case of A261049, ordered A358906.
The version for all different sums is A271619, ordered A336342.
Allowing repetition gives A305551, ordered A279787.
The version for compositions instead of partitions is A358904.
A001970 counts multisets of partitions.
A034691 counts multisets of compositions, ordered A133494.
A098407 counts sets of compositions, ordered A358907.

Programs

  • Mathematica
    Table[If[n==0,1,Sum[Binomial[PartitionsP[d],n/d],{d,Divisors[n]}]],{n,0,50}]
  • PARI
    a(n) = if (n, sumdiv(n, d, binomial(numbpart(d), n/d)), 1); \\ Michel Marcus, Dec 14 2022

Formula

a(n) = Sum_{d|n} binomial(A000041(d),n/d).

A367631 Triangle read by rows: T(n,k) is the number of permutations of length n avoiding simultaneously the patterns 123 and 132 with the maximum number of non-overlapping descents equal k.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 0, 4, 0, 0, 0, 5, 3, 0, 0, 0, 2, 14, 0, 0, 0, 0, 0, 23, 9, 0, 0, 0, 0, 0, 16, 48, 0, 0, 0, 0, 0, 0, 4, 97, 27, 0, 0, 0, 0, 0, 0, 0, 94, 162, 0, 0, 0, 0, 0, 0, 0, 0, 44, 387, 81, 0, 0, 0, 0, 0, 0, 0, 0, 8, 476, 540, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 320, 1485, 243, 0, 0, 0, 0, 0, 0
Offset: 0

Views

Author

Tian Han, Nov 24 2023

Keywords

Comments

Number of permutations of length n avoiding simultaneously the patterns 123 and 132 with the maximum number of non-overlapping descents equal k. A descent in a permutation a(1)a(2)...a(n) is position i such that a(i) > a(i+1).

Examples

			Triangle T(n,k) begins:
  1;
  1, 0;
  1, 1,  0;
  0, 4,  0,  0;
  0, 5,  3,  0,   0;
  0, 2, 14,  0,   0,    0;
  0, 0, 23,  9,   0,    0,   0;
  0, 0, 16, 48,   0,    0,   0, 0;
  0, 0,  4, 97,  27,    0,   0, 0, 0;
  0, 0,  0, 94, 162,    0,   0, 0, 0, 0;
  0, 0,  0, 44, 387,   81,   0, 0, 0, 0, 0;
  0, 0,  0,  8, 476,  540,   0, 0, 0, 0, 0, 0;
  0, 0,  0,  0, 320, 1485, 243, 0, 0, 0, 0, 0, 0;
  ...
		

Crossrefs

Row sums give A011782.
Column sums give 3*A005054.
T(2n,n) gives A133494.
T(3n+2,n) gives A000079.
T(3n+1,n) gives A053220(n+1).

Formula

G.f.: (1 + x + x^2 - 2*x^2*z - x^3*z)/(1 - 3*x^2*z - 2*x^3*z).

A034745 Dirichlet convolution of Fibonacci numbers with 3^(n-1).

Original entry on oeis.org

1, 4, 11, 33, 86, 266, 742, 2244, 6613, 19834, 59138, 177639, 531674, 1595468, 4783786, 14352225, 43048318, 129149968, 387424670, 1162288458, 3486796922, 10460430230, 31381088266, 94143408282, 282429611911, 847289262976
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[Fibonacci[n/d]*3^(d - 1), {d, Divisors[n]}], {n, 1, 25}] (* Vaclav Kotesovec, Sep 10 2019 *)

Formula

G.f.: Sum_{k>=1} 3^(k-1) * x^k/(1 - x^k - x^(2*k)). - Ilya Gutkovskiy, Jul 24 2019
a(n) ~ 3^(n-1). - Vaclav Kotesovec, Sep 11 2019

A155734 Binomial transform of A154879.

Original entry on oeis.org

3, 1, 3, 9, 27, 81, 243, 729, 2187, 6561, 19683, 59049, 177147, 531441, 1594323, 4782969, 14348907, 43046721, 129140163, 387420489, 1162261467, 3486784401, 10460353203, 31381059609, 94143178827, 282429536481, 847288609443, 2541865828329
Offset: 0

Views

Author

Paul Curtz, Jan 26 2009

Keywords

Comments

Binomial transform of the third differences of A001045.
The binomial transform of the first differences of A001045 is in A133494.
The binomial transform of the 2nd differences of A001045 is in A133494, with the sign of A133494(0) flipped.
The binomial transform of the p-th differences of A001045 is the number A077925(p-1) followed by A000244.

Crossrefs

Cf. A154879, A078008. Essentially the same as A140429 and A000244.

Programs

  • Maple
    read("transforms") ; A001045 := proc(n) option remember ; if n <= 1 then n; else procname(n-1)+2*procname(n-2) ; fi; end:
    a001045 := [seq(A001045(n),n=0..80) ] ; a154879 := DIFF(DIFF(DIFF(a001045))) ; BINOMIAL(a154879) ; # R. J. Mathar, Jul 23 2009

Formula

From Colin Barker, Apr 05 2012: (Start)
a(n) = 3*a(n-1) for n > 1.
G.f.: (3-8*x)/(1-3*x). (End)
G.f.: (1 - 2/G(0))/x where G(k) = 1 + 2^k/(1 - 2*x/(2*x + 2^k/G(k+1))); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 06 2012

Extensions

Edited and extended by R. J. Mathar, Jul 23 2009

A247936 Riordan array ((1-2x)/(1-3x), 2x).

Original entry on oeis.org

1, 1, 2, 3, 2, 4, 9, 6, 4, 8, 27, 18, 12, 8, 16, 81, 54, 36, 24, 16, 32, 243, 162, 108, 72, 48, 32, 64, 729, 486, 324, 216, 144, 96, 64, 128, 2187, 1458, 972, 648, 432, 288, 192, 128, 256, 6561, 4374, 2916, 1944, 1296, 864, 576, 384, 256, 512, 19683, 13122
Offset: 0

Views

Author

Philippe Deléham, Sep 26 2014

Keywords

Comments

Mirror of A153279.

Examples

			Triangle begins:
1
1, 2
3, 2, 4
9, 6, 4, 8
27, 18, 12, 8, 16
81, 54, 36, 24, 16, 32
243, 162, 108, 72, 48, 32, 64
Production matrix begins:
1, 2
1, 0, 2
1, 0, 0, 2
1, 0, 0, 0, 2
1, 0, 0, 0, 0, 2
1, 0, 0, 0, 0, 0, 2
1, 0, 0, 0, 0, 0, 0, 2
		

Crossrefs

Formula

Sum_{k, 0<=k<=n} T(n,k) = 3^n = A000244(n).
T(n,k) = A133494(n-k)*2^k.
T(2n,n) = A167747(n).

A336129 Number of strict compositions of divisors of n.

Original entry on oeis.org

1, 2, 4, 5, 6, 16, 14, 24, 31, 64, 66, 120, 134, 208, 360, 459, 618, 894, 1178, 1622, 2768, 3364, 4758, 6432, 8767, 11440, 15634, 24526, 30462, 42296, 55742, 75334, 98112, 131428, 168444, 258403, 315974, 432244, 558464, 753132, 958266, 1280840, 1621274
Offset: 1

Views

Author

Gus Wiseman, Jul 11 2020

Keywords

Comments

A strict composition of k is a finite sequence of distinct positive integers summing to k.

Examples

			The a(1) = 1 through a(7) = 14 compositions:
  (1)  (1)  (1)    (1)    (1)    (1)      (1)
       (2)  (3)    (2)    (5)    (2)      (7)
            (1,2)  (4)    (1,4)  (3)      (1,6)
            (2,1)  (1,3)  (2,3)  (6)      (2,5)
                   (3,1)  (3,2)  (1,2)    (3,4)
                          (4,1)  (1,5)    (4,3)
                                 (2,1)    (5,2)
                                 (2,4)    (6,1)
                                 (4,2)    (1,2,4)
                                 (5,1)    (1,4,2)
                                 (1,2,3)  (2,1,4)
                                 (1,3,2)  (2,4,1)
                                 (2,1,3)  (4,1,2)
                                 (2,3,1)  (4,2,1)
                                 (3,1,2)
                                 (3,2,1)
		

Crossrefs

Compositions of divisors are A034729.
Strict partitions of divisors are A047966.
Partitions of divisors are A047968.

Programs

  • Mathematica
    Table[Sum[Length[Join@@Permutations/@Select[IntegerPartitions[d],UnsameQ@@#&]],{d,Divisors[n]}],{n,12}]

Formula

Moebius transform is A032020 (strict compositions).
Previous Showing 61-68 of 68 results.