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 1-8 of 8 results.

A280730 Partial sums of A278742.

Original entry on oeis.org

1, 3, 6, 16, 27, 39, 59, 89, 189, 299, 499, 799, 1799, 2899, 4899, 6999, 9999, 19999, 39999, 69999, 169999, 279999, 399999, 599999, 899999, 1899999, 2999999, 4999999, 7999999, 17999999, 28999999, 48999999, 69999999, 99999999, 199999999, 399999999, 699999999
Offset: 1

Views

Author

N. J. A. Sloane, Jan 09 2017

Keywords

Crossrefs

Cf. A278742.

A278743 For a base n>1: consider the lexicographically least strictly increasing sequence c_n such that, for any m>0, Sum_{k=1..m} c_n(k) can be computed without carries in base n; the sequence c_n is (conjecturally) eventually linear, and a(n) gives its order.

Original entry on oeis.org

1, 3, 2, 5, 9, 3, 7, 4, 17, 4, 9, 15, 21, 11, 5, 11, 25, 25, 13, 7, 6, 13, 7, 29, 15, 16, 25, 7, 15, 9, 33, 17, 10, 28, 57, 8, 17, 49, 37, 19, 10, 31, 63, 21, 9, 19, 43, 41, 21, 34, 34, 69, 23, 12, 10, 21, 13, 45, 23, 51, 37, 75, 25, 13, 67, 11, 23, 42, 49, 25
Offset: 2

Views

Author

Rémy Sigrist, Nov 27 2016

Keywords

Comments

More precisely, we conjecture that, for any n>1, there are two constants k0 and b such that c_n(k + a(n)) = c_n(k)*n^b for any k>k0. [Corrected by Rémy Sigrist, Dec 24 2016]
For the values of k0 and b see A280051 and A280052. - N. J. A. Sloane, Jan 06 2017

Examples

			c_2 = A000079, and A000079 has order 1, hence a(2)=1.
c_10 = A278742, and A278742 has order 17, hence a(10)=17.
See also Links section.
		

Crossrefs

Formula

a(A000124(n)) = n for any n>0.
a(A000124(n)+1) = 2*n + 1 for any n>0.

A279732 Lexicographically least strictly increasing sequence such that, for any n>0, Sum_{k=1..n} a(k) can be computed without carries in factorial base.

Original entry on oeis.org

1, 2, 6, 8, 24, 30, 48, 120, 240, 720, 840, 1440, 1560, 5040, 10080, 15120, 40320, 45360, 80640, 120960, 362880, 403200, 725760, 1088640, 3628800, 3991680, 7257600, 7620480, 10886400, 39916800, 43545600, 79833600, 119750400, 159667200, 479001600, 958003200
Offset: 1

Views

Author

Rémy Sigrist, Dec 18 2016

Keywords

Comments

This sequence is to factorial base what A278742 is to base 10.
This sequence contains the factorial numbers (A000142); the corresponding indices are 1, 2, 3, 5, 8, 10, 14, 17, 21, 25, 30, 35, 39, 45, 49, 56, 62, 67, 74, 79, 87, 93, 102, 108, 116, 122, 131, 138, 148, 155, ...
Occasionally, the sum of the first n terms equals A033312(k) for some k;
- In that case: a(n+1)=k!, and k! divides a(m) for any m>n,
- The corresponding indices are 1, 7, 13, 34, 44, 61, 73, 101, 115, 147, 343, 387, 487, 605, 657, 788, 1226, 1296, 1575, 2986, 3586, 5152, 5260, 8236, 9173, ...
- Conjecture: this happens infinitely often.

Examples

			The first terms in base 10 and factorial base, alongside their partial sums in factorial base, are:
n    a(n)        a(n) in fact. base      Partial sum in fact. base
--   ---------   ---------------------   -------------------------
1            1                       1                         1
2            2                     1,0                       1,1
3            6                   1,0,0                     1,1,1
4            8                   1,1,0                     2,2,1
5           24                 1,0,0,0                   1,2,2,1
6           30                 1,1,0,0                   2,3,2,1
7           48                 2,0,0,0                   4,3,2,1
8          120               1,0,0,0,0                 1,4,3,2,1
9          240               2,0,0,0,0                 3,4,3,2,1
10         720             1,0,0,0,0,0               1,3,4,3,2,1
11         840             1,1,0,0,0,0               2,4,4,3,2,1
12        1440             2,0,0,0,0,0               4,4,4,3,2,1
13        1560             2,1,0,0,0,0               6,5,4,3,2,1
14        5040           1,0,0,0,0,0,0             1,6,5,4,3,2,1
15       10080           2,0,0,0,0,0,0             3,6,5,4,3,2,1
16       15120           3,0,0,0,0,0,0             6,6,5,4,3,2,1
17       40320         1,0,0,0,0,0,0,0           1,6,6,5,4,3,2,1
18       45360         1,1,0,0,0,0,0,0           2,7,6,5,4,3,2,1
19       80640         2,0,0,0,0,0,0,0           4,7,6,5,4,3,2,1
20      120960         3,0,0,0,0,0,0,0           7,7,6,5,4,3,2,1
21      362880       1,0,0,0,0,0,0,0,0         1,7,7,6,5,4,3,2,1
22      403200       1,1,0,0,0,0,0,0,0         2,8,7,6,5,4,3,2,1
23      725760       2,0,0,0,0,0,0,0,0         4,8,7,6,5,4,3,2,1
24     1088640       3,0,0,0,0,0,0,0,0         7,8,7,6,5,4,3,2,1
25     3628800     1,0,0,0,0,0,0,0,0,0       1,7,8,7,6,5,4,3,2,1
26     3991680     1,1,0,0,0,0,0,0,0,0       2,8,8,7,6,5,4,3,2,1
27     7257600     2,0,0,0,0,0,0,0,0,0       4,8,8,7,6,5,4,3,2,1
28     7620480     2,1,0,0,0,0,0,0,0,0       6,9,8,7,6,5,4,3,2,1
29    10886400     3,0,0,0,0,0,0,0,0,0       9,9,8,7,6,5,4,3,2,1
30    39916800   1,0,0,0,0,0,0,0,0,0,0     1,9,9,8,7,6,5,4,3,2,1
31    43545600   1,1,0,0,0,0,0,0,0,0,0    2,10,9,8,7,6,5,4,3,2,1
32    79833600   2,0,0,0,0,0,0,0,0,0,0    4,10,9,8,7,6,5,4,3,2,1
33   119750400   3,0,0,0,0,0,0,0,0,0,0    7,10,9,8,7,6,5,4,3,2,1
34   159667200   4,0,0,0,0,0,0,0,0,0,0   11,10,9,8,7,6,5,4,3,2,1
		

Crossrefs

Programs

  • Mathematica
    r = MixedRadix[Reverse@ Range[2, 30]]; f[a_] := Function[w, Function[s, Total@ Map[PadLeft[#, s] &, w]]@ Max@ Map[Length, w]]@ Map[IntegerDigits[#, r] &, a]; g[w_] := Times @@ Boole@ MapIndexed[#1 <= First@ #2 &, Reverse@ w] > 0; a = {1}; Do[k = Max@ a + 1; While[! g@ f@ Join[a, {k}], k++]; AppendTo[a, k], {n, 2, 16}]; a (* Michael De Vlieger, Dec 18 2016 *)

A336206 Lexicographically earliest sequence of nonnegative terms such that whenever a(k_1) = ... = a(k_m) with k_1 < ... < k_m, the sum k_1 + ... + k_m can be computed without carries in base 10.

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 3, 4, 5, 0, 0, 0, 2, 6, 6, 7, 8, 9, 10, 0, 3, 7, 11, 11, 12, 13, 14, 15, 16, 0, 3, 8, 12, 17, 17, 18, 19, 20, 21, 1, 4, 11, 13, 22, 22, 23, 24, 25, 26, 1, 7, 14, 18, 27, 28, 29, 30, 31, 32, 2, 9, 19, 33, 34, 35, 36, 37, 38, 39, 5, 15, 40, 41
Offset: 1

Views

Author

Rémy Sigrist, Jul 12 2020

Keywords

Comments

This sequence is a decimal variant of A279125.

Examples

			We can choose a(1) = a(2) = a(3) = 0 as 1 + 2 + 3 = 6 can be computed without carries.
However 1 + 2 + 3 + 4 implies a carry, so a(4) = 1.
		

Crossrefs

Programs

  • C
    See Links section.

Formula

a(n) = 0 iff n belongs to A278742.

A280731 Lexicographically least strictly increasing sequence such that, for any n>0, Sum_{k=1..n} a(k) can be computed without carries in base 9 (the numbers are written in base 10).

Original entry on oeis.org

1, 2, 3, 9, 10, 18, 19, 81, 90, 162, 171, 729, 810, 1458, 1539, 6561, 7290, 13122, 13851, 59049, 65610, 118098, 124659, 531441, 590490, 1062882, 1121931, 4782969, 5314410, 9565938, 10097379, 43046721, 47829690, 86093442, 90876411, 387420489, 430467210
Offset: 1

Views

Author

N. J. A. Sloane, Jan 09 2017

Keywords

Comments

Base 9 analog of A278742.

Crossrefs

See A281366 for these numbers written in base 9.

Programs

  • Mathematica
    LinearRecurrence[{0,0,0,9},{1,2,3,9,10,18,19},50] (* Harvey P. Dale, Feb 28 2022 *)
  • PARI
    Vec(x*(1 + 2*x + 3*x^2 + 9*x^3 + x^4 - 8*x^6) / ((1 - 3*x^2)*(1 + 3*x^2)) + O(x^50)) \\ Colin Barker, Jan 10 2017

Formula

For k>7, a(k+4) = 9*a(k).
G.f.: x*(1 + 2*x + 3*x^2 + 9*x^3 + x^4 - 8*x^6) / ((1 - 3*x^2)*(1 + 3*x^2)). - Colin Barker, Jan 10 2017

A281366 Lexicographically least strictly increasing sequence such that, for any n>0, Sum_{k=1..n} a(k) can be computed without carries in base 9 (the numbers are written in base 9).

Original entry on oeis.org

1, 2, 3, 10, 11, 20, 21, 100, 110, 200, 210, 1000, 1100, 2000, 2100, 10000, 11000, 20000, 21000, 100000, 110000, 200000, 210000, 1000000, 1100000, 2000000, 2100000, 10000000, 11000000, 20000000, 21000000, 100000000, 110000000, 200000000, 210000000
Offset: 1

Views

Author

N. J. A. Sloane, Jan 28 2017

Keywords

Comments

Base 9 analog of A278742.

Crossrefs

See A280731 for these numbers written in base 10.

Programs

  • PARI
    Vec(x*(1 + 2*x + 3*x^2 + 10*x^3 + x^4 - 9*x^6) / (1 - 10*x^4) + O(x^60)) \\ Colin Barker, Jan 29 2017

Formula

From Colin Barker, Jan 29 2017: (Start)
G.f.: x*(1 + 2*x + 3*x^2 + 10*x^3 + x^4 - 9*x^6)/(1 - 10*x^4).
a(n) = 10*a(n-4) for n>7. (End)

Extensions

More terms from Colin Barker, Jan 29 2017

A368316 Lexicographically earliest sequence of distinct nonnegative integers such that for any n >= 0, a(n) and Sum_{k = 0..n-1} a(k) can be added without carries in balanced ternary.

Original entry on oeis.org

0, 1, 2, 5, 3, 15, 4, 6, 41, 9, 18, 10, 125, 12, 16, 8, 45, 13, 14, 369, 27, 54, 28, 11, 7, 126, 17, 55, 26, 1107, 30, 51, 31, 131, 36, 46, 29, 375, 37, 44, 39, 123, 40, 42, 35, 3285, 57, 24, 135, 81, 405, 82, 38, 19, 132, 53, 1134, 84, 25, 134, 85, 23, 378
Offset: 0

Views

Author

Rémy Sigrist, Dec 21 2023

Keywords

Comments

Two integers can be added without carries in balanced ternary if they have no equal nonzero digit at the same position.
If we restrict ourselves to positive integers and allow duplicates, then we obtain A236313.
This sequence can be seen as a variant of A278742; however, the present sequence is not strictly increasing.
Will every nonnegative integer appear in the sequence?

Examples

			The first terms, alongside the balanced ternary expansions of a(n) and b(n) = Sum_{k = 0..n-1} a(k), are:
  n           |  0  1   2    3    4     5     6     7      8      9     10
  a(n)        |  0  1   2    5    3    15     4     6     41      9     18
  bter(b(n))  |  0  0   1   10  10T   11T  100T  1010   1100  100TT  101TT
  bter(a(n))  |  0  1  1T  1TT   10  1TT0    11   1T0  1TTTT    100   1T00
		

Crossrefs

Programs

  • PARI
    See Links section.

A345369 Lexicographically earliest sequence of distinct positive integers such that for any n > 0, the product of the first n terms can be computed without carry in base 10.

Original entry on oeis.org

1, 2, 3, 10, 11, 100, 101, 1000, 10000, 10001, 100000, 1000000, 10000000, 100000000, 100000001, 1000000000, 10000000000, 100000000000, 1000000000000, 10000000000000, 100000000000000, 1000000000000000, 10000000000000000, 10000000000000001, 100000000000000000
Offset: 1

Views

Author

Rémy Sigrist, Jun 16 2021

Keywords

Comments

This sequence is a variant of A278742; here we multiply, there we add.
This sequence is the union of {2, 3}, A080176 and A011557.

Examples

			The first terms, alongside their product, are:
  n   a(n)   a(1) * ... * a(n)
  --  -----  ------------------
   1      1                   1
   2      2                   2
   3      3                   6
   4     10                  60
   5     11                 660
   6    100               66000
   7    101             6666000
   8   1000          6666000000
   9  10000      66660000000000
  10  10001  666666660000000000
		

Crossrefs

Showing 1-8 of 8 results.