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 1-7 of 7 results.

A268032 Run lengths in the parity of A233312.

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 3, 1, 1, 1, 21, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 43, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 3, 1, 1, 1, 85, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 3, 1, 1, 1, 21, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 171, 1
Offset: 1

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Author

Jeremy Gardiner, Jan 24 2016

Keywords

Comments

Allowing for offset, also run lengths in the parity of A171791.
Records appear to be given by A001045 Jacobsthal numbers.
Run lengths of repeated 1's = 5,3,5,5,3,5,3,5,5,3,5, appears to be A194584.

Examples

			Parity of A233312 begins 0,1,0,1,0,1,1,1,0,1,0,1,1,1,1,1,0,1,0,1,0, ...
		

Crossrefs

A233564 c-squarefree numbers: positive integers which in binary are concatenation of distinct parts of the form 10...0 with nonnegative number of zeros.

Original entry on oeis.org

0, 1, 2, 4, 5, 6, 8, 9, 12, 16, 17, 18, 20, 24, 32, 33, 34, 37, 38, 40, 41, 44, 48, 50, 52, 64, 65, 66, 68, 69, 70, 72, 80, 81, 88, 96, 98, 104, 128, 129, 130, 132, 133, 134, 137, 140, 144, 145, 152, 160, 161, 176, 192, 194, 196, 200, 208, 256, 257, 258, 260, 261
Offset: 1

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Author

Vladimir Shevelev, Dec 13 2013

Keywords

Comments

Number of terms in interval [2^(n-1), 2^n) is the number of compositions of n with distinct parts (cf. A032020). For example, if n=6, then interval [2^5, 2^6) contains 11 terms {32,...,52}. This corresponds to 11 compositions with distinct parts of 6: 6, 5+1, 1+5, 4+2, 2+4, 3+2+1, 3+1+2, 2+3+1, 2+1+3, 1+3+2, 1+2+3.
From Gus Wiseman, Apr 06 2020: (Start)
The k-th composition in standard order (row k of 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. This sequence lists all numbers k such that the k-th composition in standard order is strict. For example, the sequence together with the corresponding strict compositions begins:
0: () 38: (3,1,2) 98: (1,4,2)
1: (1) 40: (2,4) 104: (1,2,4)
2: (2) 41: (2,3,1) 128: (8)
4: (3) 44: (2,1,3) 129: (7,1)
5: (2,1) 48: (1,5) 130: (6,2)
6: (1,2) 50: (1,3,2) 132: (5,3)
8: (4) 52: (1,2,3) 133: (5,2,1)
9: (3,1) 64: (7) 134: (5,1,2)
12: (1,3) 65: (6,1) 137: (4,3,1)
16: (5) 66: (5,2) 140: (4,1,3)
17: (4,1) 68: (4,3) 144: (3,5)
18: (3,2) 69: (4,2,1) 145: (3,4,1)
20: (2,3) 70: (4,1,2) 152: (3,1,4)
24: (1,4) 72: (3,4) 160: (2,6)
32: (6) 80: (2,5) 161: (2,5,1)
33: (5,1) 81: (2,4,1) 176: (2,1,5)
34: (4,2) 88: (2,1,4) 192: (1,7)
37: (3,2,1) 96: (1,6) 194: (1,5,2)
(End)

Examples

			49 in binary has the following parts of the form 10...0 with nonnegative number of  zeros: (1),(1000),(1). Two of them are the same. So it is not in the sequence. On the other hand, 50 has distinct parts (1)(100)(10), thus it is a term.
		

Crossrefs

A subset of A333489 and superset of A333218.
All of the following pertain to compositions in standard order (A066099):
- Length is A000120.
- Weighted sum is A029931.
- Partial sums from the right are A048793.
- Sum is A070939.
- Runs are counted by A124767.
- Reversed initial intervals A164894.
- Initial intervals are A246534.
- Constant compositions are A272919.
- Strictly decreasing compositions are A333255.
- Strictly increasing compositions are A333256.
- Anti-runs are counted by A333381.
- Anti-runs are A333489.

Programs

  • Mathematica
    bitPatt[n_]:=bitPatt[n]=Split[IntegerDigits[n,2],#1>#2||#2==0&];
    Select[Range[0,300],bitPatt[#]==DeleteDuplicates[bitPatt[#]]&] (* Peter J. C. Moses, Dec 13 2013 *)
    stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    Select[Range[0,100],UnsameQ@@stc[#]&] (* Gus Wiseman, Apr 04 2020 *)

Extensions

More terms from Peter J. C. Moses, Dec 13 2013
0 prepended by Gus Wiseman, Apr 04 2020

A124771 Number of distinct subsequences for compositions in standard order.

Original entry on oeis.org

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

Views

Author

Keywords

Comments

The standard order of compositions is given by A066099.
From Vladimir Shevelev, Dec 18 2013: (Start)
Every number in binary is a concatenation of parts of the form 10...0 with k>=0 zeros. For example, 5=(10)(1), 11=(10)(1)(1), 7=(1)(1)(1). We call d>0 a c-divisor of m, if d consists of some consecutive parts of m taking from the left to the right. Note that, to d=0 corresponds an empty set of parts. So it is natural to consider 0 as a c-divisor of every m. For example, 5=(10)(1) is a divisor of 23=(10)(1)(1)(1). Analogously, 1,2,3,7,11,23 are c-divisors of 23. But 6=(1)(10) is not a c-divisor of 23.
One can prove a one-to-one correspondence between distinct subsequences for composition no. n in standard order and c-divisors of n. So, the sequence lists also numbers of c-divisors of nonnegative integers.
(End)
These are contiguous subsequences, or restrictions to a subinterval. The case for all subsequences is A334299. - Gus Wiseman, Jun 02 2020

Examples

			Composition number 11 is 2,1,1; the subsequences are (empty); 1; 2; 1,1; 2,1; 2,1,1; so a(11) = 6.
The table starts:
1
2
1 2
1 3 3 3
Let n=11=(10)(1)(1). We have the following c-divisors of 11: 0,1,2,3,5,11. Thus a(11)=6. Note, that 3=(1)(1) is not a c-divisor of 13=(1)(10)(1) since, although it contains parts of 3=(1)(1), but in non-consecutive order. The c-divisors of 13 are 0,1,2,5,6,13. So, a(13)=6.
From _Gus Wiseman_, Jun 01 2020: (Start)
The c-divisors of n are given in column n below:
  0  0  0  0  0  0  0  0  0  0  0   0   0   0   0   0   0   0   0
     1  2  1  4  1  1  1  8  1  2   1   1   1   1   1   16  1   2
           3     2  2  3     4  10  2   4   2   2   3       8   4
                 5  6  7     9      3   12  5   3   7       17  18
                                    5       6   6   15
                                    11      13  14
(End)
		

Crossrefs

Cf. A000005, A011782 (row lengths), A066099, A114994, A233249, A233312.
Not allowing empty subsequences gives A124770.
Dominates A333257.
The case for not just contiguous subsequences is A334299.
Positions of first appearances are A335279.
Compositions where every subinterval has a different sum are A333222.
Knapsack compositions are A333223.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    Table[Length[Union[ReplaceList[stc[n],{_,s___,_}:>{s}]]],{n,0,100}] (* Gus Wiseman, Jun 01 2020 *)

Formula

a(n) = A124770(n) + 1.
From Vladimir Shevelev, Dec 18 2013: (Start)
a(2^n) = 2. Note that in concatenation representations of integers in binary, numbers {2^k}, k>=0, play the role of primes. So the formula is an analog of A000005(prime(n))=2.
a(2^n-1) = n+1; for n>=2, a(2^n+1) = 4.
For c-equivalent numbers n_1 and n_2 (i.e., differed only by order of parts) we have a(n_1) = a(n_2). For example, a(24)=a(17)=4. If the canonical representation of n is n=(1)^k_1[*](10)^k_2[*](100)^k_3[*]... , where [*] denotes operation of concatenation (cf. A233569), then a(n)<=(k_1+1)*(k_2+1)*...
(End)

A162439 Write down the binary representation of n. Partition the string which is this binary representation by placing a '+' just left of every 1. Add the resulting base 2 numbers. a(n) = decimal equivalent of this sum.

Original entry on oeis.org

1, 2, 2, 4, 3, 3, 3, 8, 5, 4, 4, 5, 4, 4, 4, 16, 9, 6, 6, 6, 5, 5, 5, 9, 6, 5, 5, 6, 5, 5, 5, 32, 17, 10, 10, 8, 7, 7, 7, 10, 7, 6, 6, 7, 6, 6, 6, 17, 10, 7, 7, 7, 6, 6, 6, 10, 7, 6, 6, 7, 6, 6, 6, 64, 33, 18, 18, 12, 11, 11, 11, 12, 9, 8, 8, 9, 8, 8, 8, 18, 11, 8, 8, 8, 7, 7, 7, 11, 8, 7, 7, 8, 7, 7
Offset: 1

Views

Author

Leroy Quet, Jul 03 2009

Keywords

Comments

From Vladimir Shevelev, Dec 11 2014: (Start)
Or, sum of parts of the form 10...0 with nonnegative number of zeros in binary representation of n as the corresponding powers of 2. For example, n=50 in binary is a concatenation of parts (1)(100)(10). Then a(50)=1+4+2=7.
Every positive number k occurs a finite number of times, such that the position of the last appearance of k is 2^k-1.
Moreover, the number of times of appearances of k is the number of compositions of k into powers of 2, i.e., it is A023359(k), k>0. (End)

Examples

			52 in binary is 110100. Placing the +'s before every 1, we get +1+10+100, which is 1+2+4 = 7 in decimal. So a(52) = 7.
		

Crossrefs

Programs

  • Maple
    a:= proc(n) local l, s, i, j; l:= convert(n, base, 2); s:= 0; i:=1; for j from nops(l)-1 to 1 by -1 do if l[j]=0 then i:= i*2; else s:= s+i; i:= 1 fi od; s+i end: seq(a(n), n=1..150); # Alois P. Heinz, Jul 28 2009
    Lton := proc(L) local i ; add(op(i,L)*2^(i-1),i=1..nops(L)) ; end: A162439 := proc(n) local a,lef,b2,ri ; a := 0 ; lef := 0; b2 := convert(n,base,2) ; for ri from lef+1 do if op(ri,b2) = 1 then a := a+Lton([op(lef+1..ri,b2)]) ; lef := ri ; fi; if ri =nops(b2) then break; fi; od: a ; end: seq(A162439(n),n=1..100) ; # R. J. Mathar, Jul 30 2009
  • Mathematica
    a[n_] := FromDigits[#, 2]& /@ Split[IntegerDigits[n, 2] , #2==0&] // Total; Array[a, 100] (* Jean-François Alcover, Jan 07 2016 *)

Formula

Let, for k_1>k_2>...>k_r, n = 2^k_1 + 2^k_2 +...+ 2^k_r. Then a(n) = 2^(k_1-k_2-1) + 2^(k_2-k_3-1) + 2^(k_(r-1)-k_r-1) + 2^k_r. - Vladimir Shevelev, Dec 11 2013

Extensions

More terms from Alois P. Heinz and R. J. Mathar, Jul 28 2009

A233420 Minimal number of c-squares (A020330) and/or 1's which add to n.

Original entry on oeis.org

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

Views

Author

Vladimir Shevelev, Dec 09 2013

Keywords

Comments

Conjecture: the sequence is bounded by a constant.

Examples

			For n=33, we have 33=15+15+3. Since 33 is not in union of {1} and c-squares and is not a sum of two such numbers, then a(33)=3.
		

Crossrefs

Programs

  • PARI
    v=vector(10^5,n,n+n<<#binary(n)); \\ choose large enough that v[#v] > n for a(n) below.
    a(n)=if(setsearch(v,n),return(1));if(n<3,return(n));my(where=setsearch(v,n+1,1),t=n);if(!where,where=setsearch(v,n,1));forstep(i=where-1,1,-1,t=min(w(n-v[i]),t); if(t==1,return(2))); t+1 \\ Charles R Greathouse IV, Dec 10 2013

A235669 Sum of parts of the form 10...0 and 20...0 with nonnegative number of zeros in ternary representation of n as the corresponding numbers 3^n and 2*3^n.

Original entry on oeis.org

0, 1, 2, 3, 2, 3, 6, 3, 4, 9, 4, 5, 4, 3, 4, 7, 4, 5, 18, 7, 8, 5, 4, 5, 8, 5, 6, 27, 10, 11, 6, 5, 6, 9, 6, 7, 10, 5, 6, 5, 4, 5, 8, 5, 6, 19, 8, 9, 6, 5, 6, 9, 6, 7, 54, 19, 20, 9, 8, 9, 12, 9, 10, 11, 6, 7, 6, 5, 6, 9, 6, 7, 20, 9, 10, 7, 6, 7, 10, 7, 8, 81, 28, 29, 12
Offset: 0

Views

Author

Vladimir Shevelev, Jan 13 2014

Keywords

Comments

The number of appearances of k is the number of compositions of k into numbers of the form 3^n and 2*3^n, A235684(k).

Crossrefs

Programs

  • Mathematica
    bitPatt[n_,b_]:=Split[IntegerDigits[n,b ],#2==0&]; Map[Plus@@Map[FromDigits[#,3]&,bitPatt[#,3]]&,Range[0,50]] (* Peter J. C. Moses, Jan 13 2014 *)

A267508 Smallest number "c-equivalent" to n.

Original entry on oeis.org

1, 2, 3, 4, 5, 5, 7, 8, 9, 10, 11, 9, 11, 11, 15, 16, 17, 18, 19, 18, 21, 21, 23, 17, 19, 21, 23, 19, 23, 23, 31, 32, 33, 34, 35, 36, 37, 37, 39, 34, 37, 42, 43, 37, 43, 43, 47, 33, 35, 37, 39, 37, 43, 43, 47, 35, 39, 43, 47, 39, 47, 47, 63, 64, 65, 66, 67, 68, 69, 69, 71, 68, 73
Offset: 1

Views

Author

Jörgen Backelin, Jan 16 2016

Keywords

Comments

For c-equivalence, see the comments to A233249. Briefly put, two positive integers m and n are c-equivalent in the sense of Vladimir Shevelev, if they have ordinary binary representations with the same multisets of substrings resulting from cutting the full strings immediately before each bit 1. A(n) is defined as the smallest positive integer, which is c-equivalent to n. Alternatively, in the manners of A114994, the lengths of these substrings can be considered as representing ways to write integers as sums of positive integers with arbitrarily ordered sums, and a(n) as the unique integer whose corresponding substring lengths form the corresponding integer partition.
For instance, the ordinary binary representations of 11, 13, and 14 are 1011, 1101, and 1110, respectively, which yields the equal multisets {"10","1","1"}, and {"1","10","1"}, and {"1","1","10"} of strings, respectively; whence 11, 13, and 14 are c-equivalent.
A(n) is an odd number if and only if the substring "1" appears at least once in the multiset. Since this is the case if and only if it also holds for the binary representation of n concatenated with itself, and A233312(n) = a(m) for the number m whose binary representation is this concatenation, we have a(n) == A233312(n) (mod 2) for all n. Moreover, empirical data has suggested that perhaps A233312(n)+1 == A171791(n+1) (mod 2) for all n >= 1. This relation holds in general if and only if a(n)+1 == A171791(n+1) for the same n, which in its turn is true if and only if the relation with fibbinary numbers first empirically observed by Paul D. Hanna in the comments to A171791 holds in general.
The sequence A163382 also maps n to a c-equivalent integer <=n; however, here, only cyclic permutations of the sequences of substrings are allowed. Thus, a more restricted equivalence relation is used; whence a(n) <= A163382(n) for all n. Equality holds for infinitely many n, including n = 1..37.

Examples

			The set of integers c-equivalent to 38 is {37,38,41,44,50,52} (with the binary representations 100101, 100110, 101001, 101100, 110010, and 110100, respectively). The smallest of these numbers is 37. Thus, a(38) = 37. Alternatively, the substrings of 100110_binary = 38 correspond to writing 6 as the sum of 3+1+2, which is a permutation of the partition 6 = 3+2+1, where the right hand side corresponds to 37. (On the other hand, only 41 and 52 may be achieved from 38 by cyclic permutations of the bits, whence A163382(38) = 38.)
		

Crossrefs

A114994 = range(a), A233312(n) = a(A020330(n)).
Showing 1-7 of 7 results.