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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A332904 Sum of distinct integers encountered on all possible paths from n to 1 when iterating with nondeterministic map k -> k - k/p, where p is any of the prime factors of k.

Original entry on oeis.org

1, 3, 6, 7, 12, 16, 23, 15, 25, 30, 41, 36, 49, 57, 66, 31, 48, 63, 82, 66, 105, 99, 122, 76, 91, 115, 90, 125, 154, 156, 187, 63, 222, 114, 240, 139, 176, 196, 217, 138, 179, 251, 294, 215, 264, 284, 331, 156, 300, 213, 258, 247, 300, 220, 345, 261, 334, 348, 407, 336, 397, 429, 395, 127, 492, 512, 579, 246, 650, 546, 617, 291, 364
Offset: 1

Views

Author

Antti Karttunen, Apr 04 2020

Keywords

Examples

			a(12): we have three alternative paths: {12, 8, 4, 2, 1}, {12, 6, 4, 2, 1} or {12, 6, 3, 2, 1}, with numbers [1, 2, 3, 4, 6, 8, 12] present, therefore a(12) = 1+2+3+4+6+8+12 = 36.
For n=15 we have five alternative paths from 15 to 1: {15, 10, 5, 4, 2, 1}, {15, 10, 8, 4, 2, 1}, {15, 12, 8, 4, 2, 1},  {15, 12, 6, 4, 2, 1},  {15, 12, 6, 3, 2, 1}. These form a lattice illustrated below:
        15
       / \
      /   \
    10     12
    / \   / \
   /   \ /   \
  5     8     6
   \__  |  __/|
      \_|_/   |
        4     3
         \   /
          \ /
           2
           |
           1,
therefore a(15) = 1+2+3+4+5+6+8+10+12+15 = 66.
		

Crossrefs

Cf. A333790 (sum of the route with minimal sum), A333794.

Programs

  • Mathematica
    Total /@ Nest[Function[{a, n}, Append[a, Union@ Flatten@ Table[Append[a[[n - n/p]], n], {p, FactorInteger[n][[All, 1]]}]]] @@ {#, Length@ # + 1} &, {{1}}, 72] (* Michael De Vlieger, Apr 15 2020 *)
  • PARI
    up_to = 20000;
    A332904list(up_to) = { my(v=vector(up_to)); v[1] = Set([1]); for(n=2,up_to, my(f=factor(n)[, 1]~, s=Set([n])); for(i=1,#f,s = setunion(s,v[n-(n/f[i])])); v[n] = s); apply(vecsum,v); }
    v332904 = A332904list(up_to);
    A332904(n) = v332904[n];

Formula

For all primes p, a(p) = a(p-1) + p.
For all n >= 1, A333000(n) >= a(n) >= A333794(n) >= A333790(n).

A049115 a(n) is the number of iterations of the Euler phi function needed to reach a power of 2, when starting from n.

Original entry on oeis.org

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

Views

Author

Keywords

Comments

a(n) = A227944(n) if n is not a power of 2. - Eric M. Schmidt, Oct 13 2013

Examples

			If n is a power of 2, then a(n)=0 by definition. If n = 59049, then by iterating with phi, we get 59049 -> 39366 -> 13122 -> 4374 -> 1458 -> 486 -> 162 -> 54 -> 18 -> 6 -> 2 -> 1. It took ten steps to reach the first power of 2 (2 in this case), so a(59049) = 10.
		

Crossrefs

Programs

  • Mathematica
    Table[If[IntegerQ@ Log2@ n, 0, -1 + Length@ NestWhileList[EulerPhi, n, ! IntegerQ@ Log2@ # &]], {n, 105}] (* Michael De Vlieger, Aug 01 2017 *)
  • PARI
    A049115(n) = if(!bitand(n,n-1),0,1+A049115(eulerphi(n))); \\ Antti Karttunen, Aug 28 2021

Formula

The smallest x so that Nest[ EulerPhi, n, x ] = 2^w is just achieved.
From Antti Karttunen, Aug 28 2021: (Start)
If A209229(n) = 1, then a(n) = 0, otherwise a(n) = 1 + a(A000010(n)).
a(n) <= A003434(n) and a(n) <= A329697(n) for all n.
(End)

Extensions

Definition corrected and simplified, example corrected by Antti Karttunen, Aug 28 2021

A334144 Consider the mapping k -> (k - (k/p)), where prime p | k. a(n) = maximum distinct terms at any position j among the various paths to 1.

Original entry on oeis.org

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

Views

Author

Keywords

Comments

Let i = A064097(n) be the common path length and let 1 <= j <= i. Given a path P, we find for any j relatively few distinct values. Regarding a common path length i, see A333123 comment 2, and proof at A064097.
Maximum term in row n of A334184.

Examples

			For n=15, the paths are shown vertically at left, and the graph obtained appears at right:
  15   15   15   15   15  =>         15
   |    |    |    |    |            _/ \_
   |    |    |    |    |           /     \
  10   10   12   12   12  =>     10       12
   |    |    |    |    |         | \_   _/ |
   |    |    |    |    |         |   \ /   |
   5    8    6    6    8  =>     5    8    6
   |    |    |    |    |          \_  |  _/|
   |    |    |    |    |            \_|_/  |
   4    4    3    4    4  =>          4    3
   |    |    |    |    |              |  _/
   |    |    |    |    |              |_/
   2    2    2    2    2  =>          2
   |    |    |    |    |              |
   |    |    |    |    |              |
   1    1    1    1    1  =>          1
Because the maximum number of distinct terms in any row is 3, a(15) = 3.
		

Crossrefs

Programs

  • Mathematica
    Max[Length@ Union@ # & /@ Transpose@ #] & /@ Nest[Function[{a, n}, Append[a, Join @@ Table[Flatten@ Prepend[#, n] & /@ a[[n - n/p]], {p, FactorInteger[n][[All, 1]]}]]] @@ {#, Length@ # + 1} &, {{{1}}}, 105]
    (* Second program: *)
    g[n_] := Block[{lst = {{n}}}, While[lst[[-1]] != {1}, lst = Join[lst, {Union@ Flatten[# - #/(First@ # & /@ FactorInteger@ #) & /@ lst[[-1]] ]}]]; Max[Length /@ lst]]; Array[g, 105] (* Robert G. Wilson v, May 08 2020 *)

A175125 a(n) is the number of numbers m such that the number of iterations of r -> r - (largest divisor d < r) needed to reach 1 starting at r = m is equal to n.

Original entry on oeis.org

1, 1, 2, 3, 5, 9, 13, 23, 36, 65, 100, 175, 275, 468, 760, 1266, 2077, 3454, 5690, 9449, 15547, 25709, 42459, 70181, 115947, 191509, 316570, 523087, 864406, 1428174, 2359266
Offset: 0

Views

Author

Jaroslav Krizek, Feb 15 2010

Keywords

Examples

			Example (a(4)=5): There are five numbers (7,9,10,12,16) with 4 steps of defined iteration: 7-1=6, 6-3=3, 3-1=2, 2-1=1; 9-3=6, 6-3=3, 3-1=2, 2-1=1; 10-5=5, 5-1=4, 4-2=2, 2-1=1; 12-6=6, 6-3=3, 3-1=2, 2-1=1; 16-8=8, 8-4=4, 4-2=2, 2-1=1.
		

Crossrefs

Programs

  • PARI
    a064097(n)={my(k=1,d=divisors(n),r=n-d[#d-1]);while(r>1,d=divisors(r);r-=d[#d-1];k++);k};
    my(c=vector(50));for(k=2,2^20,j=a064097(k);c[j]++);concat([1],c[1..20]) \\ Hugo Pfoertner, Mar 23 2020

Extensions

a(8)-a(27) from Hugo Pfoertner, Mar 23 2020
a(28)-a(30) from Robert G. Wilson v, Apr 05 2020

A334200 Fully additive with a(n) = n-1 for n <= 3, and a(p) = 1 + a(A048673(p)) when p is prime > 3 and a(n*m) = a(n) + a(m) when m,n > 1.

Original entry on oeis.org

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

Views

Author

Antti Karttunen, May 13 2020

Keywords

Crossrefs

Cf. also A064097, A334206.

Programs

  • PARI
    A334200(n) = if(n<=3, n-1, if(isprime(n), 1+A334200((1+nextprime(1+n))/2), my(f=factor(n)); (apply(A334200, f[, 1])~ * f[, 2])));

A332810 Number of integers in range 1..n that are not encountered on any of the possible paths from n to 1 when iterating with nondeterministic map k -> k - k/p, where p is any prime factor of k.

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 1, 4, 3, 4, 4, 5, 5, 5, 5, 11, 11, 9, 9, 12, 9, 12, 12, 15, 16, 15, 17, 16, 16, 16, 16, 26, 16, 26, 17, 24, 24, 24, 24, 30, 30, 25, 25, 31, 27, 31, 31, 37, 31, 38, 37, 38, 38, 40, 39, 41, 40, 41, 41, 42, 42, 42, 43, 57, 43, 43, 43, 58, 43, 46, 46, 57, 57, 57, 54, 58, 47, 58, 58, 68, 66, 68, 68, 62, 69, 62, 62, 72, 72
Offset: 1

Views

Author

Antti Karttunen, Apr 04 2020

Keywords

Examples

			a(12): we have three alternative paths: {12, 8, 4, 2, 1}, {12, 6, 4, 2, 1} or {12, 6, 3, 2, 1}, with [5, 7, 9, 10, 11] being the only numbers in range 1..12 that do not occur in any of those paths, therefore a(12) = 5.
		

Crossrefs

Programs

  • PARI
    up_to = 105;
    A332809list(up_to) = { my(v=vector(up_to)); v[1] = Set([1]); for(n=2,up_to, my(f=factor(n)[, 1]~, s=Set([n])); for(i=1,#f,s = setunion(s,v[n-(n/f[i])])); v[n] = s); apply(length,v); }
    v332809 = A332809list(up_to);
    A332810(n) = (n-v332809[n]);

Formula

a(n) = n - A332809(n).

A332992 Maximum outdegree in the graph formed by a subset of numbers in range 1 .. n with edge relation k -> k - k/p, where p can be any of the prime factors of k.

Original entry on oeis.org

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

Views

Author

Antti Karttunen, Apr 04 2020

Keywords

Comments

Maximum number of distinct prime factors of any one integer encountered on all possible paths from n to 1 when iterating with nondeterministic map k -> k - k/p, where p can be any of the prime factors of k.

Examples

			For n=15 we have five alternative paths from 15 to 1: {15, 10, 5, 4, 2, 1}, {15, 10, 8, 4, 2, 1}, {15, 12, 8, 4, 2, 1},  {15, 12, 6, 4, 2, 1},  {15, 12, 6, 3, 2, 1}. These form a lattice illustrated below:
        15
       / \
      /   \
    10     12
    / \   / \
   /   \ /   \
  5     8     6
   \__  |  __/|
      \_|_/   |
        4     3
         \   /
          \ /
           2
           |
           1
With edges going from 15 towards 1, the maximum outdegree is 2, which occurs at nodes 15, 12, 10 and 6, therefore a(15) = 2.
		

Crossrefs

Cf. A002110 (positions of records and the first occurrence of each n).

Programs

  • Mathematica
    With[{s = Nest[Function[{a, n}, Append[a, Join @@ Table[Flatten@ Prepend[#, n] & /@ a[[n - n/p]], {p, FactorInteger[n][[All, 1]]}]]] @@ {#, Length@ # + 1} &, {{{1}}}, 105]}, Array[If[# == 1, 0, Max@ Tally[#][[All, -1]] &@ Union[Join @@ Map[Partition[#, 2, 1] &, s[[#]] ]][[All, 1]] ] &, Length@ s]] (* Michael De Vlieger, May 02 2020 *)
  • PARI
    up_to = 105;
    A332992list(up_to) = { my(v=vector(up_to)); v[1] = 0; for(n=2,up_to, v[n] = max(omega(n),vecmax(apply(p -> v[n-n/p], factor(n)[, 1]~)))); (v); };
    v332992 = A332992list(up_to);
    A332992(n) = v332992[n];

Formula

a(n) = max(A001221(n), {Max a(n - n/p), for p prime and dividing n}).
For all odd primes p, a(p) = a(p-1).
For all n >= 0, a(A002110(n)) = n.

A352957 Triangle read by rows: Row n is the lexicographically earliest strictly monotonic completely additive sequence of length n.

Original entry on oeis.org

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

Views

Author

Peter Munn, Apr 11 2022

Keywords

Comments

Each sequence consists of nonnegative integers indexed from 1.
Note in particular in the formula section, the lower bound, floor(n/k), for first differences between terms in a row. This follows (using the additive property) from the strict monotonicity of floor(n/k)+1 consecutive terms near the end of the row.
For any k, with increasing length n >= k, the first k terms of the sequences approach similarity with a real-valued logarithmic function defined on the integers. For example, the asymptote of T(n,3)/T(n,2) is log(3)/log(2), A020857.

Examples

			(For row 4.) A completely additive sequence requires T(4,1) = 0. Strict monotonicity requires T(4,4) > T(4,3) > T(4,2). So T(4,4) >= T(4,2) + 2. Using the additivity this becomes T(4,2) + T(4,2) >= T(4,2) + T(4,1) + 2. Subtracting T(4,2) and substituting 0 for T(4,1) we get T(4,2) >= 2. So from T(4,4) > T(4,3) > T(4,2), we see T(4,3) >= 3, T(4,4) >= 4. So row 4 = (0, 2, 3, 4) as it is strictly monotonic and completely additive and from the preceding arguments is seen to be the lexicographically earliest such.
Triangle starts:
0;
0, 1;
0, 1,  2;
0, 2,  3,  4;
0, 2,  3,  4,  5;
0, 3,  5,  6,  7,  8;
0, 3,  5,  6,  7,  8,  9;
0, 4,  6,  8,  9, 10, 11, 12;
0, 5,  8, 10, 11, 13, 14, 15, 16;
0, 5,  8, 10, 12, 13, 14, 15, 16, 17;
0, 5,  8, 10, 12, 13, 14, 15, 16, 17, 18;
0, 7, 11, 14, 16, 18, 19, 21, 22, 23, 24, 25;
0, 7, 11, 14, 16, 18, 19, 21, 22, 23, 24, 25, 26;
0, 7, 11, 14, 16, 18, 20, 21, 22, 23, 24, 25, 26, 27;
0, 8, 13, 16, 19, 21, 23, 24, 26, 27, 28, 29, 30, 31, 32;
0, 9, 14, 18, 21, 23, 25, 27, 28, 30, 31, 32, 33, 34, 35, 36;
		

Crossrefs

Cf. A020857.
Completely additive sequences, s, with primes p mapped to a function of s(p-1) and maybe s(p+1): A064097, A344443, A344444; and for functions of earlier terms, see A334200.
For completely additive sequences with primes p mapped to a function of p, see A001414.
For completely additive sequences with prime(k) mapped to a function of k, see A104244.
For completely additive sequences where some primes are mapped to 1, the rest to 0 (notably, some ruler functions) see the cross-references in A249344.

Formula

The definition specifies: T(n,j*k) = T(n,j) + T(n,k); for k > 1, T(n,k) > T(n,k-1).
T(n,1) = 0, otherwise T(n,k) >= T(n,k-1) + floor(n/k).
For prime p, T(p,p) = T(p-1,p-1) + 1, otherwise T(p,k) = T(p-1,k).
T(n,2) >= 2*floor(n/4) + floor(n/9).
T(n,3) >= ceiling( (3*T(n,2) + floor(n/9)) / 2).
T(11,k) = A344443(k).
For k <> 13, T(23,k) = A344444(k).

A117618 Least number with complexity height of n, under integer complexity A005245.

Original entry on oeis.org

1, 6, 7, 10, 22, 683
Offset: 1

Views

Author

Jonathan Vos Post, Apr 07 2006

Keywords

Comments

Consider the recursion: A005245(n), A005245(A005245(n)), A005245(A005245(A005245(n))), ... which we know is finite before reaching a fixed point, as A005245(n) <= n. The number of steps needed to reach such a fixed point is the complexity height of n (with respect to the A005245 measure of complexity, there being others in the OEIS).
a(7) >= 872573642639 = A005520(89). - David A. Corneth, May 06 2024

Examples

			a(1) = 1 because the A005245 complexity of 1 is 1, already giving a fixed point.
a(2) = 6 because it is the smallest x such that A005245(x) =/= x and A005245(x) = A005245(A005245(x)).
a(3) = 7 because 7 is the least number x with complexity 6, thus taking a further step of recursion to reach a fixed point.
a(4) = 10 because 10 is the least number with complexity 7.
a(5) = 22 because 22 is the least number with complexity 10.
a(6) = 683 because 683 is the least number with complexity 22.
a(7) = the least number with complexity 683.
		

References

  • W. A. Beyer, M. L. Stein and S. M. Ulam, The Notion of Complexity. Report LA-4822, Los Alamos Scientific Laboratory of the University of California, Los Alamos, NM, December 1971.
  • R. K. Guy, Unsolved Problems in Number Theory, Sect. F26.

Crossrefs

Formula

a(n) = least k such that A005245^(n)(k) = A005245^(n-1)(k) but (if n>1) A005245^(n-1)(k) != A005245^(n-2)(k), where ^ denotes repeated application.
For n >= 3, a(n) = A005520(a(n-1)). - Max Alekseyev, May 06 2024

Extensions

a(2)=6 inserted by Giovanni Resta, Jun 15 2016
Edited by Max Alekseyev, May 06 2024

A191614 The lexicographically earliest sequence such that a(n) - a(n-1) is the largest proper divisor of a(n).

Original entry on oeis.org

1, 2, 3, 6, 7, 14, 21, 42, 43, 86, 129, 258, 301, 602, 903, 1806, 1849, 3698, 5547, 11094, 12943, 25886, 38829, 77658, 77659, 155318, 232977, 465954, 543613, 1087226, 1630839, 3261678, 3339337, 6678674, 10018011, 20036022, 23375359, 46750718, 70126077, 140252154
Offset: 1

Views

Author

Jaroslav Krizek, Jun 09 2011

Keywords

Comments

In contrast, A000079(n) is the lexicographically *largest* sequence such that a(n) - a(n-1) is the largest proper divisor of a(n).
Sequence is infinite because A060681 is surjective.

Crossrefs

Programs

  • Maple
    A191614 := proc(n) option remember; if n = 1 then 1; else for m from 1 do if m-A032742(m) = procname(n-1) then return m; end if; end do: end if; end proc: # R. J. Mathar, Jun 13 2011
  • PARI
    p=0; for (v=1, 140252154, if (v%(v-p)==0 && (p==0 || (d=divisors(v))[#d-1]==v-p), print1 (p=v ", "))) \\ Rémy Sigrist, Apr 24 2021

Formula

a(n) is the smallest number m such that m - A032742(m) = a(n-1), n > 1.

Extensions

More terms from Rémy Sigrist, Apr 24 2021
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