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 1-10 of 17 results. Next

A001422 Numbers which are not the sum of distinct squares.

Original entry on oeis.org

2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 27, 28, 31, 32, 33, 43, 44, 47, 48, 60, 67, 72, 76, 92, 96, 108, 112, 128
Offset: 1

Views

Author

N. J. A. Sloane, Jeff Adams (jeff.adams(AT)byu.net)

Keywords

Comments

This is the complete list (Sprague).

References

  • S. Lin, Computer experiments on sequences which form integral bases, pp. 365-370 of J. Leech, editor, Computational Problems in Abstract Algebra. Pergamon, Oxford, 1970.
  • Harry L. Nelson, The Partition Problem, J. Rec. Math., 20 (1988), 315-316.
  • J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 222.

Crossrefs

Complement of A003995. Subsequence of A004441.
Cf. A025524 (number of numbers not the sum of distinct n-th-order polygonal numbers)
Cf. A007419 (largest number not the sum of distinct n-th-order polygonal numbers)
Cf. A053614, A121405 (corresponding sequences for triangular and pentagonal numbers)
Cf. A001476, A046039, A194768, A194769 for 3rd, 4th, 5th, 6th powers.
Cf. A001661.

Programs

  • Mathematica
    nn=50; t=Rest[CoefficientList[Series[Product[(1+x^(k*k)), {k,nn}], {x,0,nn*nn}], x]]; Flatten[Position[t,0]] (* T. D. Noe, Jul 24 2006 *)
  • PARI
    select( is_A001422(n,m=n)={m^2>n&& m=sqrtint(n); n!=m^2&&!while(m>1,isSumOfSquares(n-m^2,m--)&&return)}, [1..128]) \\ M. F. Hasler, Apr 21 2020

A030052 Smallest number whose n-th power is a sum of distinct smaller positive n-th powers.

Original entry on oeis.org

3, 5, 6, 15, 12, 25, 40, 84, 47, 63, 68, 81, 102, 95, 104, 162, 123
Offset: 1

Views

Author

Richard C. Schroeppel

Keywords

Comments

Sprague has shown that for any n, all sufficiently large integers are the sum of distinct n-th powers. Sequence A001661 lists the largest number not of this form, so we know that a(n) is less than or equal to the next larger n-th power. - M. F. Hasler, May 25 2020
a(18) <= 200, a(19) <= 234, a(20) <= 242; for more upper bounds see the Al Zimmermann's Programming Contests link: The "Final Report" gives exact solutions for n = 16 through 30; those for n = 16 and 17 have been confirmed to be minimal by Jeremy Sawicki. - M. F. Hasler, Jul 20 2020

Examples

			3^1 = 2^1 + 1^1, and there is no smaller solution given that the r.h.s. is the smallest possible sum of distinct positive powers.
For n = 2, one sees immediately that 3 is not a solution (3^2 > 2^2 + 1^2) and one can check that 4^2 isn't equal to Sum_{x in A} x^2 for any subset A of {1, 2, 3}. Therefore, the well known hypotenuse number 5 (cf. A009003) with 5^2 = 4^2 + 3^2 provides the smallest possible solution.
a(17) = 123 since 123^17 = Sum {3, 5, 7, 8, 9, 11, 13, 16, 17, 19, 30, 33, 34, 35, 38, 40, 41, 43, 51, 52, 54, 55, 58, 59, 60, 63, 66, 69, 70, 71, 72, 73, 75, 76, 81, 86, 87, 88, 89, 90, 92, 95, 98, 106, 107, 108, 120}^17, with obvious notation. [Solution found by Jeremy Sawicki on July 3, 2020, see Al Zimmermann's Programming Contests link.] - _M. F. Hasler_, Jul 18 2020
For more examples, see the link.
		

Crossrefs

Other sequences defined by sums of distinct n-th powers: A001661, A364637.

Programs

  • PARI
    A030052(n, m=n\/log(2)+1, s=0)={if(!s, until(A030052(n, m, (m+=1)^n),), s < 2^n || s > (m+n+1)*m^n\(n+1), m=s<2, m=min(sqrtnint(s, n), m); s==m^n || until( A030052(n, m-1, s-m^n) || (s>=(m+n)*(m-=1)^n\(n+1) && !m=0), )); m} \\ Does exhaustive search to find the least solution m. Use optional 2nd arg to specify a starting value for m. Calls itself with nonzero 3rd (optional) argument: in this case, returns nonzero iff s is the sum of powers <= m^n. - For illustration only: takes very long already for n = 8 and n >= 10. - M. F. Hasler, May 25 2020

Formula

a(n) <= A001661(n)^(1/n) + 1. - M. F. Hasler, May 25 2020
a(n) >= A332101(n) = A078607(n)+2 (conjectured). - M. F. Hasler, May 25 2020

Extensions

a(8)-a(10) found by David W. Wilson
a(11) from Al Zimmermann, Apr 07 2004
a(12) from Al Zimmermann, Apr 13 2004
a(13) from Manol Iliev, Jan 04 2010
a(14) and a(15) from Manol Iliev, Apr 28 2011
a(16) and a(17) due to Jeremy Sawicki, added by M. F. Hasler, Jul 20 2020

A332065 Infinite square array where row n lists the integers whose n-th power is the sum of distinct n-th powers of positive integers; read by falling antidiagonals.

Original entry on oeis.org

3, 4, 5, 5, 7, 6, 6, 9, 9, 15, 7, 10, 12, 25, 12, 8, 11, 13, 27, 23, 25, 9, 12, 14, 29, 24, 28, 40, 10, 13, 15, 30, 28, 32, 43, 84, 11, 14, 16, 31, 29, 34, 44, 85, 47, 12, 15, 17, 33, 30, 35, 45, 86, 49, 63, 13, 16, 18, 35, 31, 36, 46, 87, 52, 64, 68
Offset: 1

Views

Author

M. F. Hasler, Mar 31 2020

Keywords

Comments

Each row contains all sufficiently large integers (Sprague). Sequences A001422, A001476, A046039, A194768, A194769, ... mention the largest number which can't be written as sum of distinct n-th powers for n = 2, 3, 4, 5, 6, ...; see also A001661. Sequence A332066 gives the number of positive integers not in row n.
All positive multiples of any T(n,k) appear later in that row (because if s^n = Sum_{x in S} x^n, then (k*s)^n = Sum_{x in k*S} x^n).

Examples

			The table reads: (Entries from where on T(n,k+1) = T(n,k)+1 are marked by *.)
   n | k=1    2    3    4    5    6    7    8    9   10   11   12   13  ...
  ---+---------------------------------------------------------------------
   1 |   3*   4    5    6    7    8    9   10   11   12   13   14   15  ...
   2 |   5    7    9*  10   11   12   13   14   15   16   17   18   19  ...
   3 |   6    9   12*  13   14   15   16   17   18   19   20   21   22  ...
   4 |  15   25   27   29   30   31   33   35   37   39   41   43   45* ...
   5 |  12   23   24   28*  29   30   31   32   33   34   35   36   37  ...
   6 |  25   28   32   34*  35   36   37   38   39   40   41   42   43  ...
   7 |  40   43*  44   45   46   47   48   49   50   51   52   53   54  ...
   8 |  84*  85   86   87   88   89   90   91   92   93   94   95   96  ...
   9 |  47   49   52*  53   54   55   56   57   58   59   60   61   62  ...
  10 |  63*  64   65   66   67   68   69   70   71   72   73   74   75  ...
  11 |  68   73*  74   75   76   77   78   79   80   81   82   83   84  ...
  ...| ...
Row 1: 3^1 = 2^1 + 1^1, 4^1 = 3^1 + 1^1, 5^1 = 4^1 + 1^1, 6^1 = 5^1 + 1^1, ...
Row 2: 5^2 = 4^2 + 3^2, 7^2 = 6^2 + 3^2 + 2^2, 9^2 = 8^2 + 4^2 + 1^2, ...
Row 3: 6^3 = 5^3 + 4^3 + 3^3, 9^3 = 8^3 + 6^3 + 1, 12^3 = 10^3 + 8^3 + 6^3, ...
Row 4: 15^4 = Sum {14, 9, 8, 6, 4}^4, 25^4 = Sum {21, 20, 12, 10, 8, 6, 2}^4, ...
See the link for other rows.
		

Crossrefs

Cf. A030052 (first column), A001661.
Cf. A009003 (hypotenuse numbers; subsequence of row 2).
Cf. A332066.

Programs

  • PARI
    M332065=Map(); A332065(n,m,r)={if(r, if( m<2^n||m>r^n*(r+n+1)\(n+1), m<2, r=min(sqrtnint(m,n),r), m==r^n || while( !A332065(n,m-r^n,r-=1) && (mA004736(n),n=A002260(n)]; mapisdefined(M332065,[n,m],&r), r, n<2, m+2, r=if(m>1,A332065(n,m-1),n+2); until(A332065(n, (r+=1)^n, r-1),); mapput(M332065,[n,m],r); r)} \\ Calls itself with nonzero (optional) 3rd argument to find by exhaustive search whether r can be written as sum of distinct powers <= m^n. (Comment added by M. F. Hasler, May 25 2020)

Formula

T(1,k) = 2 + k for all k. (Indeed, s^1 = (s-1)^1 + 1 and s-1 > 1 for s > 2.)
T(2,k) = 6 + k for all k >= 3. (Use s^2 = (s-1)^2 + 2*s-1 and A001422, A009003.)
T(3,k) = 9 + k for all k >= 3. (Use max A001476 = 12758 < 24^3.)
T(4,k) = 32 + k for all k >= 13. (Use max A046039 < 48^4.)
T(5,k) = 24 + k for all k >= 4. (Use max(N \ A194768) < 37^5.)
T(6,k) = 30 + k for all k >= 4. (Use max(N \ A194769) < 48^6.)
T(7,k) = 41 + k for all k >= 2.
T(9,k) = 49 + k for all k >= 3.

Extensions

More terms from M. F. Hasler, Jul 19 2020

A276517 Indices k such that A276516(k) = 0.

Original entry on oeis.org

2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 41, 43, 44, 45, 46, 47, 48, 53, 54, 60, 61, 67, 70, 72, 74, 76, 79, 82, 84, 87, 90, 92, 93, 96, 105, 106, 107, 108, 111, 112, 114, 117, 122, 128, 133, 135, 139, 141, 148, 159
Offset: 1

Views

Author

Vaclav Kotesovec, Dec 12 2016

Keywords

Comments

This is different from A001422, first difference: a(14) = 25, A001422(14) = 27.
Conjecture: for k > 7169 there are no more terms in this sequence (tested for k < 10000000).

Examples

			3 is in the sequence because A276516(3) = 0
4 is not in the sequence because A276516(4) = -1
4222 is in the sequence because A276516(4222) = 0
7169 is in the sequence because A276516(7169) = 0
		

Crossrefs

Programs

  • Mathematica
    nn = 100; A276516 = Rest[CoefficientList[Series[Product[(1-x^(k^2)), {k, nn}], {x, 0, nn^2}], x]]; Select[Range[nn^2], A276516[[#]]==0&]
    nmax = 10000; nn = Floor[Sqrt[nmax]]+1; poly = ConstantArray[0, nn^2 + 1]; poly[[1]] = 1; poly[[2]] = -1; poly[[3]] = 0; Do[Do[poly[[j + 1]] -= poly[[j - k^2 + 1]], {j, nn^2, k^2, -1}];, {k, 2, nn}]; A276516 = Take[poly, {2, nmax+1}]; Select[Range[nmax], A276516[[#]]==0&]

A121571 Largest number that is not the sum of n-th powers of distinct primes.

Original entry on oeis.org

6, 17163, 1866000
Offset: 1

Views

Author

T. D. Noe, Aug 08 2006

Keywords

Comments

As stated by Sierpinski, H. E. Richert proved a(1) = 6. Dressler et al. prove a(2) = 17163.
Fuller & Nichols prove T. D. Noe's conjecture that a(3) = 1866000. They also prove that 483370 positive numbers cannot be written as the sum of cubes of distinct primes. - Robert Nichols, Sep 08 2017
Noe conjectures that a(4) = 340250525752 and that 31332338304 positive numbers cannot be written as the sum of fourth powers of distinct primes. - Charles R Greathouse IV, Nov 04 2017

Examples

			a(1) = 6 because only the numbers 1, 4 and 6 are not the sum of distinct primes.
		

References

  • W. Sierpinski, Elementary Theory of Numbers, Warsaw, 1964, p. 143-144.

Crossrefs

Cf. A231407 (numbers that are not the sum of distinct primes).
Cf. A121518 (numbers that are not the sum of squares of distinct primes).
Cf. A213519 (numbers that are the sum of cubes of distinct primes).
Cf. A001661 (integers instead of primes).

Formula

a(1) = A231407(3), a(2) = A121518(2438). - Jonathan Sondow, Nov 26 2013

A279486 Indices k such that A279484(k) = 0.

Original entry on oeis.org

2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 66, 67, 68, 69, 70, 71, 74, 75, 76, 77
Offset: 1

Views

Author

Vaclav Kotesovec, Dec 13 2016

Keywords

Comments

This is different from A001476, first difference: a(450) = 540, A001476(450) = 542.
Conjecture: for k > 353684 there are no more terms in this sequence (tested for k < 1000000).

Examples

			3 is in the sequence because A279484(3) = 0
8 is not in the sequence because A279484(8) = -1
344739 is in the sequence because A279484(344739) = 0
353684 is in the sequence because A279484(353684) = 0
		

Crossrefs

Programs

  • Mathematica
    nn = 10; A279484 = Rest[CoefficientList[Series[Product[(1-x^(k^3)), {k, nn}], {x, 0, nn^3}], x]]; Select[Range[nn^3], A279484[[#]]==0&]
    nmax = 1000; nn = Floor[nmax^(1/3)]+1; poly = ConstantArray[0, nn^3 + 1]; poly[[1]] = 1; poly[[2]] = -1; poly[[3]] = 0; Do[Do[poly[[j + 1]] -= poly[[j - k^3 + 1]], {j, nn^3, k^3, -1}];, {k, 2, nn}]; A279484 = Take[poly, {2, nmax+1}]; Select[Range[nmax], A279484[[#]]==0&]

A003999 Sums of distinct nonzero 4th powers.

Original entry on oeis.org

1, 16, 17, 81, 82, 97, 98, 256, 257, 272, 273, 337, 338, 353, 354, 625, 626, 641, 642, 706, 707, 722, 723, 881, 882, 897, 898, 962, 963, 978, 979, 1296, 1297, 1312, 1313, 1377, 1378, 1393, 1394, 1552, 1553, 1568, 1569, 1633, 1634, 1649, 1650, 1921, 1922
Offset: 1

Views

Author

Keywords

Comments

5134240 is the largest positive integer not in this sequence. - Jud McCranie
If we tightened the sequence requirement so that the sum was of more than one 4th power, we would remove exactly 32 4th powers from the terms: row 4 of A332065 indicates which 4th powers would remain. After a(1) = 1, the next number in this sequence that is in the analogous sequences for cubes and squares is a(24) = 881 = A364637(4). - Peter Munn, Aug 01 2023

References

  • The Penguin Dictionary of Curious and Interesting Numbers, David Wells, entry 5134240.

Crossrefs

Cf. A046039 (complement).
Cf. A003995, A003997, A194768, A194769 (analogs for squares, cubes, 5th and 6th powers).
A217844 is a subsequence.

Programs

  • Maple
    (1+x)*(1+x^16)*(1+x^81)*(1+x^256)*(1+x^625)*(1+x^1296)*(1+x^2401)*(1+x^4096)*(1+x^6561)*(1+x^10000)
  • Mathematica
    max = 2000; f[x_] := Product[1 + x^(k^4), {k, 1, 10}]; Exponent[#, x]& /@ List @@ Normal[Series[f[x], {x, 0, max}]] // Rest (* Jean-François Alcover, Nov 09 2012, after Charles R Greathouse IV *)
  • PARI
    upto(lim)={
        lim\=1;
        my(v=List(),P=prod(n=1,lim^(1/4),1+x^(n^4),1+O(x^(lim+1))));
        for(n=1,lim,if(polcoeff(P,n),listput(v,n)));
        Vec(v)
    }; \\ Charles R Greathouse IV, Sep 02 2011

Formula

For n > 4244664, a(n) = n + 889576. - Charles R Greathouse IV, Sep 02 2011

A194768 Sum of distinct positive fifth powers.

Original entry on oeis.org

1, 32, 33, 243, 244, 275, 276, 1024, 1025, 1056, 1057, 1267, 1268, 1299, 1300, 3125, 3126, 3157, 3158, 3368, 3369, 3400, 3401, 4149, 4150, 4181, 4182, 4392, 4393, 4424, 4425, 7776, 7777, 7808, 7809, 8019, 8020, 8051, 8052, 8800, 8801, 8832, 8833, 9043, 9044, 9075, 9076
Offset: 1

Views

Author

Keywords

Comments

From Peter Munn, Aug 02 2023: (Start)
67898771 = A001661(5) is the largest number not in the sequence.
After a(1) = 1, the next term that is in all the analogous sequences for smaller powers is a(35) = 7809 = A364637(5).
If we tightened the sequence requirement so that the sum was of more than one 5th power, we would remove exactly 24 5th powers from the terms: row 5 of A332065 indicates which 5th powers would remain.
(End)

Crossrefs

Cf. A000584 (5th powers), A001661, A332065, A364637.
Cf. A003997, A003999, A194769 (analogs for 3rd, 4th and 6th powers).
A217845 is a subsequence.

Programs

  • Maple
    N:= 2*10^4: # to get all terms <= N
    S:= {0}:
    for i from 1 while i^5 <= N do
      S:= select(`<=`, map(`+`,S,i^5),N) union S
    od:
    sort(convert(S minus {0},list)); # Robert Israel, Jun 26 2019
  • PARI
    upto(lim)={
        lim\=1;
        my(v=List(),P=prod(n=1,lim^(1/5),1+x^(n^5),1+O(x^(lim+1))));
        for(n=1,lim,if(polcoeff(P,n),listput(v,n)));
        Vec(v)
    }; \\ Charles R Greathouse IV, Sep 02 2011

Formula

For n > 53986089, a(n) = n + 13912682. [Charles R Greathouse IV, Sep 02 2011]

Extensions

Name qualified by Peter Munn, Aug 02 2023

A194769 Sum of distinct nonzero sixth powers.

Original entry on oeis.org

1, 64, 65, 729, 730, 793, 794, 4096, 4097, 4160, 4161, 4825, 4826, 4889, 4890, 15625, 15626, 15689, 15690, 16354, 16355, 16418, 16419, 19721, 19722, 19785, 19786, 20450, 20451, 20514, 20515, 46656, 46657, 46720, 46721, 47385, 47386, 47449, 47450, 50752, 50753, 50816
Offset: 1

Views

Author

Keywords

Comments

See A001661 for a proof of the formula. - M. F. Hasler, May 15 2020
From Peter Munn, Aug 02 2023: (Start)
11146309947 = A001661(6) is the largest number not in the sequence.
After a(1) = 1, the next term that is in all the analogous sequences for smaller powers is a(86) = 134067 = A364637(6).
If we tightened the sequence requirement so that the sum was of more than one 6th power, we would remove exactly 30 6th powers from the terms: row 6 of A332065 indicates which 6th powers would remain.
(End)

Crossrefs

A217846 is a subsequence.
Cf. A003997, A003999, A194768 (analogs for 3rd, 4th and 5th powers).

Programs

  • PARI
    upto(lim)={
        lim\=1;
        my(v=List(),P=prod(n=1,lim^(1/6),1+x^(n^6),1+O(x^(lim+1))));
        for(n=1,lim,if(polcoeff(P,n),listput(v,n)));
        Vec(v)
    }

Formula

For n > 9108736851, a(n) = n + 2037573096.

Extensions

More terms from David A. Corneth, Apr 21 2020
Name qualified by Peter Munn, Aug 02 2023

A279487 Indices k such that A279485(k) = 0.

Original entry on oeis.org

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70
Offset: 1

Views

Author

Vaclav Kotesovec, Dec 13 2016

Keywords

Comments

This is different from A046039, first difference: a(14328) = 14979, A046039(14328) = 14981.
Conjecture: Last term is a(1040799) = 64674419. For k > 64674419 there are no more terms in this sequence (tested for k < 150000000).
Last terms are: 30082710, 30345655, 30358709, 30530388, 30982210, 31463972, 32369456, 32374194, 32594966, 32658048, 32780596, 32875172, 32997892, 33135812, 33440935, 33647428, 34086978, 34112787, 34629875, 35535908, 35638453, 36081828, 36140868, 36945332, 39218566, 39581363, 40364547, 40491526, 41235157, 43853600, 47973011, 57353782, 57767766, 64674419

Examples

			3 is in the sequence because A279485(3) = 0
16 is not in the sequence because A279485(16) = -1
57767766 is in the sequence because A279485(57767766) = 0
64674419 is in the sequence because A279485(64674419) = 0
		

Crossrefs

Programs

  • Mathematica
    nn = 10; A279485 = Rest[CoefficientList[Series[Product[(1-x^(k^4)), {k, nn}], {x, 0, nn^4}], x]]; Select[Range[nn^4], A279485[[#]]==0&]
    nmax = 10000; nn = Floor[nmax^(1/4)]+1; poly = ConstantArray[0, nn^4 + 1]; poly[[1]] = 1; poly[[2]] = -1; poly[[3]] = 0; Do[Do[poly[[j + 1]] -= poly[[j - k^4 + 1]], {j, nn^4, k^4, -1}];, {k, 2, nn}]; A279485 = Take[poly, {2, nmax+1}]; Select[Range[nmax], A279485[[#]]==0&]
Showing 1-10 of 17 results. Next