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 31 results. Next

A178132 Partial sums of A003995.

Original entry on oeis.org

0, 1, 5, 10, 19, 29, 42, 56, 72, 89, 109, 130, 155, 181, 210, 240, 274, 309, 345, 382, 420, 459, 499, 540, 582, 627, 673, 722, 772, 823, 875, 928, 982, 1037, 1093, 1150, 1208, 1267, 1328, 1390, 1453, 1517, 1582, 1648, 1716, 1785, 1855, 1926, 1999, 2073, 2148
Offset: 0

Views

Author

Jonathan Vos Post, May 20 2010

Keywords

Comments

Partial sums of sum of (any number of) distinct squares. The subsequence of primes in this partial sum begins: 5, 19, 29, 89, 109, 499, 673, 823, 1093, 1453, 1999, 2543, 2963.

Examples

			a(13) = 0 + 1 + 4 + 5 + 9 + 10 + 13 + 14 + 16 + 17 + 20 + 21 + 25 + 26 = 181 is prime.
		

Crossrefs

Formula

a(n) = SUM[i=0..n] A003995(i) = SUM[i=0..n] (r^2 + s^2 + t^2+ ...) with 0<=r

A033461 Number of partitions of n into distinct squares.

Original entry on oeis.org

1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 2, 2, 0, 0, 2, 2, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 1, 0, 0, 2, 2, 0, 0, 2, 3, 1, 1, 2, 2, 1, 1, 1, 1, 1, 0, 2, 3, 1, 1, 4, 3, 0, 1, 2, 2, 1, 0, 1, 4, 3, 0, 2, 4, 2, 1, 3, 2, 1, 2, 3, 3, 2, 1, 3, 6, 3, 0, 2, 5, 3, 0, 1, 3, 3, 3, 4
Offset: 0

Keywords

Comments

"WEIGH" transform of squares A000290.
a(n) = 0 for n in {A001422}, a(n) > 0 for n in {A003995}. - Alois P. Heinz, May 14 2014
Number of partitions of n in which each part i has multiplicity i. Example: a(50)=3 because we have [1,2,2,3,3,3,6,6,6,6,6,6], [1,7,7,7,7,7,7,7], and [3,3,3,4,4,4,4,5,5,5,5,5]. - Emeric Deutsch, Jan 26 2016
The Heinz numbers of integer partitions into distinct pairs are given by A324587. - Gus Wiseman, Mar 09 2019
From Gus Wiseman, Mar 09 2019: (Start)
Equivalent to Emeric Deutsch's comment, a(n) is the number of integer partitions of n where the multiplicities (where if x < y the multiplicity of x is counted prior to the multiplicity of y) are equal to the distinct parts in increasing order. The Heinz numbers of these partitions are given by A109298. For example, the first 30 terms count the following integer partitions:
1: (1)
4: (22)
5: (221)
9: (333)
10: (3331)
13: (33322)
14: (333221)
16: (4444)
17: (44441)
20: (444422)
21: (4444221)
25: (55555)
25: (4444333)
26: (555551)
26: (44443331)
29: (5555522)
29: (444433322)
30: (55555221)
30: (4444333221)
The case where the distinct parts are taken in decreasing order is A324572, with Heinz numbers given by A324571.
(End)

Examples

			a(50)=3 because we have [1,4,9,36], [1,49], and [9,16,25]. - _Emeric Deutsch_, Jan 26 2016
From _Gus Wiseman_, Mar 09 2019: (Start)
The first 30 terms count the following integer partitions:
   1: (1)
   4: (4)
   5: (4,1)
   9: (9)
  10: (9,1)
  13: (9,4)
  14: (9,4,1)
  16: (16)
  17: (16,1)
  20: (16,4)
  21: (16,4,1)
  25: (25)
  25: (16,9)
  26: (25,1)
  26: (16,9,1)
  29: (25,4)
  29: (16,9,4)
  30: (25,4,1)
  30: (16,9,4,1)
(End)
		

References

  • James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, pages 288-289.

Crossrefs

Cf. A001422, A003995, A078434, A242434 (the same for compositions), A279329.
Row sums of A341040.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           b(n, i-1) +`if`(i^2>n, 0, b(n-i^2, i-1))))
        end:
    a:= n-> b(n, isqrt(n)):
    seq(a(n), n=0..100);  # Alois P. Heinz, May 14 2014
  • Mathematica
    nn=10; CoefficientList[Series[Product[(1+x^(k*k)), {k,nn}], {x,0,nn*nn}], x] (* T. D. Noe, Jul 24 2006 *)
    b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, b[n, i-1] + If[i^2 > n, 0, b[n - i^2, i-1]]]]; a[n_] := b[n, Floor[Sqrt[n]]]; Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Sep 21 2015, after Alois P. Heinz *)
    nmax = 20; poly = ConstantArray[0, nmax^2 + 1]; poly[[1]] = 1; poly[[2]] = 1; Do[Do[poly[[j + 1]] += poly[[j - k^2 + 1]], {j, nmax^2, k^2, -1}];, {k, 2, nmax}]; poly (* Vaclav Kotesovec, Dec 09 2016 *)
    Table[Length[Select[IntegerPartitions[n],Reverse[Union[#]]==Length/@Split[#]&]],{n,30}] (* Gus Wiseman, Mar 09 2019 *)
  • PARI
    a(n)=polcoeff(prod(k=1,sqrt(n),1+x^k^2), n)
    
  • PARI
    first(n)=Vec(prod(k=1,sqrtint(n),1+'x^k^2,O('x^(n+1))+1)) \\ Charles R Greathouse IV, Sep 03 2015
    
  • Python
    from functools import cache
    from sympy.core.power import isqrt
    @cache
    def b(n,i):
      # Code after Alois P. Heinz
      if n == 0: return 1
      if i == 0: return 0
      i2 = i*i
      return b(n, i-1) + (0 if i2 > n else b(n - i2, i-1))
    a = lambda n: b(n, isqrt(n))
    print([a(n) for n in range(1, 101)]) # Darío Clavijo, Nov 30 2023

Formula

G.f.: Product_{n>=1} ( 1+x^(n^2) ).
a(n) ~ exp(3 * 2^(-5/3) * Pi^(1/3) * ((sqrt(2)-1)*zeta(3/2))^(2/3) * n^(1/3)) * ((sqrt(2)-1)*zeta(3/2))^(1/3) / (2^(4/3) * sqrt(3) * Pi^(1/3) * n^(5/6)), where zeta(3/2) = A078434. - Vaclav Kotesovec, Dec 09 2016
See Murthy, Brack, Bhaduri, Bartel (2018) for a more complete asymptotic expansion. - N. J. A. Sloane, Aug 17 2018

Extensions

More terms from Michael Somos

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

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

A004432 Numbers that are the sum of 3 distinct nonzero squares.

Original entry on oeis.org

14, 21, 26, 29, 30, 35, 38, 41, 42, 45, 46, 49, 50, 53, 54, 56, 59, 61, 62, 65, 66, 69, 70, 74, 75, 77, 78, 81, 83, 84, 86, 89, 90, 91, 93, 94, 98, 101, 104, 105, 106, 107, 109, 110, 113, 114, 115, 116, 117, 118, 120, 121, 122, 125, 126, 129, 131, 133
Offset: 1

Keywords

Comments

Numbers that can be written as a(n) = x^2 + y^2 + z^2 with 0 < x < y < z.
This is a subsequence (equal to the range) of A024803. As a set, it is the union of A025339 and A024804, subsequences of numbers having exactly one, resp. more than one, such representations. - M. F. Hasler, Jan 25 2013
Conjecture: a number n is a sum of 3 squares, but not a sum of 3 distinct nonzero squares (i.e., is in A004432 but not A000408), if and only if it is of the form 4^j*s, where j >= 0 and s in {1, 2, 3, 5, 6, 9, 10, 11, 13, 17, 18, 19, 22, 25, 27, 33, 34, 37, 43, 51, 57, 58, 67, 73, 82, 85, 97, 99, 102, 123, 130, 163, 177, 187, 193, 267, 627, 697}. - Jeffrey Shallit, Jan 15 2017
4*a(n) gives the sums of 3 distinct nonzero even squares. - Wesley Ivan Hurt, Apr 05 2021

Examples

			14 = 1^2 + 2^2 + 3^2;
62 = 1^2 + 5^2 + 6^2.
		

Programs

  • Haskell
    a004432 n = a004432_list !! (n-1)
    a004432_list = filter (p 3 $ tail a000290_list) [1..] where
       p k (q:qs) m = k == 0 && m == 0 ||
                      q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)
    -- Reinhard Zumkeller, Apr 22 2013
  • Mathematica
    f[upto_]:=Module[{max=Floor[Sqrt[upto]]},Select[Union[Total/@ (Subsets[ Range[ max],{3}]^2)],#<=upto&]]; f[150]  (* Harvey P. Dale, Mar 24 2011 *)
  • PARI
    is_A004432(n)=for(x=1,sqrtint(n\3),for(y=x+1,sqrtint((n-1-x^2)\2),issquare(n-x^2-y^2)&return(1)))  \\ M. F. Hasler, Feb 02 2013
    

Formula

A004432 = { x^2 + y^2 + z^2; 0 < x < y < z }.
n is in A004432 <=> A025442(n) > 0. - M. F. Hasler, Feb 03 2013

A004433 Numbers that are the sum of 4 distinct nonzero squares: of form w^2+x^2+y^2+z^2 with 0

Original entry on oeis.org

30, 39, 46, 50, 51, 54, 57, 62, 63, 65, 66, 70, 71, 74, 75, 78, 79, 81, 84, 85, 86, 87, 90, 91, 93, 94, 95, 98, 99, 102, 105, 106, 107, 109, 110, 111, 113, 114, 116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 129, 130, 131, 133, 134, 135, 137
Offset: 1

Keywords

Examples

			30 = 1^2+2^2+3^2+4^2.
		

Programs

  • Haskell
    a004433 n = a004433_list !! (n-1)
    a004433_list = filter (p 4 $ tail a000290_list) [1..] where
       p k (q:qs) m = k == 0 && m == 0 ||
                      q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)
    -- Reinhard Zumkeller, Apr 22 2013
    
  • Mathematica
    data = Flatten[ DeleteCases[ FindInstance[ w^2 + x^2 + y^2 + z^2 == # && 0 < w < x < y < z < #, {w, x, y, z}, Integers] & /@ Range[137], {}], 1]; w^2 + x^2 + y^2 + z^2 /. data (* Ant King, Oct 17 2010 *)
    Select[Union[Total[#^2]&/@Subsets[Range[10],{4}]],#<=137&] (* Harvey P. Dale, Jul 03 2011 *)
  • PARI
    list(lim)=my(v=List([30, 39, 46, 50, 51, 54, 57, 62, 63, 65, 66, 70, 71, 74, 75, 78, 79, 81, 84, 85, 86, 87, 90, 91, 93, 94, 95, 98, 99, 102, 105, 106, 107, 109, 110, 111, 113, 114, 116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 129, 130, 131, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 145, 146, 147, 149, 150, 151, 153, 154, 155, 156]), u=[160, 168, 172, 176, 188, 192, 208, 220, 224, 232, 240, 256, 268, 272, 288, 292, 304, 320, 328, 352, 368, 384, 388, 400, 412, 416, 432, 448, 496, 512, 528, 544, 576, 592, 608], t=1); if(lim<156, return(select(k->k<=lim, Vec(v)))); for(n=158,lim\1, if(n#u, t=1)); Vec(v) \\ Charles R Greathouse IV, Jan 08 2025

Formula

{n: A025443(n) >=1}. Union of A025386 and A025376. - R. J. Mathar, Jun 15 2018
a(n) = n + O(log n). - Charles R Greathouse IV, Jan 08 2025

A097563 Least integer that can be written as a sum of zero or more distinct squares in exactly n ways, or -1 if no such number exists.

Original entry on oeis.org

2, 0, 25, 50, 65, 94, 90, 110, 155, 126, 191, 170, 186, 174, 190, 211, 195, 226, 210, 231, 234, 235, 332, 255, 283, 259, 274, 275, 270, 323, 310, 286, 306, 299, 330, 381, 295, 347, 334, 319, 315, 331, 405, 339, 335, 364, 359, 351, 367, 387, 371, 370, 404, 438
Offset: 0

Author

Isabel C. Lugo (izzycat(AT)gmail.com), Aug 27 2004

Keywords

Comments

a(n) = -1 for almost all n. Conjecture: for n > 34189857569982621, this sequence is the integers > 37163, in order, interspersed with -1s. - Charles R Greathouse IV, Sep 04 2015

Examples

			a(4) = 65 because we can write 65 as a sum of distinct squares in four ways: 65 = 8^2 + 1^2 = 7^2 + 4^2 = 6^2 + 5^2 + 2^2 = 6^2 + 4^2 + 3^2 + 2^2 and we cannot do this with any smaller integer.
a(0) = 2 because we cannot write 2 as a sum of distinct squares and it is the smallest number with this property.
		

Crossrefs

First occurrence of n in A033461; see also A001422 (0 ways) and A003995 (1 or more ways).

Programs

  • Maple
    gf := product(1+x^F(k), k=1..31); ser := series(gf, x=0, 1001); S := [seq(coeff(ser,x^(1*i)),i=1..1000)]; A := proc(i); x := 0; for j from 1 to nops(a) while x = 0 do > if a[j] = i then x := 1; fi; od; j-1; end; seq(A(n), n=1..67);

Extensions

Edited by Ray Chandler, Sep 01 2004

A003997 Sums of distinct positive cubes.

Original entry on oeis.org

1, 8, 9, 27, 28, 35, 36, 64, 65, 72, 73, 91, 92, 99, 100, 125, 126, 133, 134, 152, 153, 160, 161, 189, 190, 197, 198, 216, 217, 224, 225, 243, 244, 251, 252, 280, 281, 288, 289, 307, 308, 315, 316, 341, 342, 343, 344, 349, 350, 351, 352, 368, 369, 370, 371
Offset: 1

Keywords

Comments

12758 is the largest of 2788 positive integers not in this sequence. - Jud McCranie, Dec 11 1999

References

  • D. Wells, The Penguin Dictionary of Curious and Interesting Numbers, entry 12758.

Crossrefs

Complement of A001476. Cf. A003995.

Programs

  • Maple
    GF := series( (1+x)*(1+x^8)*(1+x^27)*(1+x^64)*(1+x^125)*(1+x^216)*(1+x^343)*(1+x^512)*(1+x^729)*(1+x^1000), x, 11^3); # Edited by M. F. Hasler, May 01 2020
    A003997_upto := n -> map(degree,{op(convert(series(product(1 + x^(k^3), k = 1 .. floor(root(n,3)))-1, x, n+1),`+`))});  # M. F. Hasler, May 01 2020;
  • Mathematica
    lim = 8; s = {0}; Do[s = Union[s, s + n^3], {n, lim}]; Select[s, 0 < # <= lim^3 &] (* T. D. Noe, Jul 10 2012 *)
  • PARI
    list(lim)={
        lim\=1;
        my(lm=min(lim+1,12758), v=List(), P);
        P=prod(n=1,lm^(1/3),1+x^(n^3),1+O(x^lm));
        for(n=1,lm-1,if(polcoeff(P,n),listput(v,n)));
        if(lim>12758,concat(Vec(v),vector(lim-12758,i,i+12758)),Vec(v))
    }; \\ Charles R Greathouse IV, Sep 02 2011
    
  • PARI
    select( is_A003997(n,m=n)={m^3>n&&m=sqrtnint(n,3);n==m^3||while(m>1,is_A003997(n-m^3,m--)&&return(1))}, [1..400]) \\ M. F. Hasler, Apr 21 2020

Formula

For n > 9970, a(n) = n + 2788. - Charles R Greathouse IV, Sep 02 2011

Extensions

Definition clarified by Jeppe Stig Nielsen, Jan 27 2015

A004434 Numbers that are the sum of 5 distinct nonzero squares.

Original entry on oeis.org

55, 66, 75, 79, 82, 87, 88, 90, 94, 95, 99, 100, 103, 106, 110, 111, 114, 115, 118, 120, 121, 123, 126, 127, 129, 130, 131, 132, 134, 135, 138, 139, 142, 143, 144, 145, 146, 147, 148, 150, 151, 152, 154, 155, 156, 157, 158, 159, 160, 162, 163
Offset: 1

Keywords

Programs

  • Haskell
    a004434 n = a004434_list !! (n-1)
    a004434_list = filter (p 5 $ tail a000290_list) [1..] where
       p k (q:qs) m = k == 0 && m == 0 ||
                      q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)
    -- Reinhard Zumkeller, Apr 22 2013
  • PARI
    upto(lim)=my(v=List(), tb, tc, td, te); for(a=5, sqrt(lim), for(b=4, min(a-1, sqrt(lim-a^2)), tb=a^2+b^2; for(c=3, min(b-1, sqrt(lim-tb)), tc=tb+c^2; for(d=2, min(c-1, sqrt(lim-tc)), td=tc+d^2; for(e=1, d-1, te=td+e^2; if(te>lim, break,listput(v, te))))))); vecsort(Vec(v), , 8) \\ Charles R Greathouse IV, Jul 17 2011
    

Formula

a(n) = n + 124 for n > 121. - Charles R Greathouse IV, Jul 17 2011

A224981 Numbers that are the sum of exactly 6 distinct nonzero squares.

Original entry on oeis.org

91, 104, 115, 119, 124, 130, 131, 136, 139, 143, 146, 147, 151, 152, 154, 155, 156, 159, 160, 163, 164, 166, 167, 168, 169, 170, 171, 175, 176, 178, 179, 180, 181, 182, 184, 187, 188, 190, 191, 192, 194, 195, 196, 199, 200, 201, 202, 203, 204, 206, 207, 208
Offset: 1

Author

Reinhard Zumkeller, Apr 22 2013

Keywords

Examples

			a(1) = 1 + 4 + 9 + 16 + 25 + 36 = 91 = A000330(6);
a(2) = 1 + 4 + 9 + 16 + 25 + 49 = 104;
a(3) = 1 + 4 + 9 + 16 + 36 + 49 = 115;
a(4) = 1 + 4 + 9 + 16 + 25 + 64 = 119;
a(5) = 1 + 4 + 9 + 25 + 36 + 49 = 124.
		

Programs

  • Haskell
    a224981 n = a224981_list !! (n-1)
    a224981_list = filter (p 6 $ tail a000290_list) [1..] where
       p k (q:qs) m = k == 0 && m == 0 ||
                      q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)
  • Mathematica
    nmax = 1000;
    S[n_] := S[n] = Union[Total /@ Subsets[
         Range[Floor[Sqrt[n]]]^2, {6}]][[1 ;; nmax]];
    S[nmax];
    S[n = nmax + 1];
    While[S[n] != S[n - 1], n++];
    S[n] (* Jean-François Alcover, Nov 20 2021 *)

A224982 Numbers that are the sum of exactly 7 distinct nonzero squares.

Original entry on oeis.org

140, 155, 168, 172, 179, 185, 188, 191, 195, 196, 200, 203, 204, 205, 211, 212, 215, 217, 219, 220, 224, 225, 227, 230, 231, 232, 233, 235, 236, 239, 240, 243, 244, 245, 246, 247, 248, 251, 252, 254, 256, 257, 259, 260, 263, 264, 265, 267, 268, 269, 270, 271
Offset: 1

Author

Reinhard Zumkeller, Apr 22 2013

Keywords

Examples

			a(1) = 1 + 4 + 9 + 16 + 25 + 36 + 49 = 140 = A000330(7);
a(2) = 1 + 4 + 9 + 16 + 25 + 36 + 64 = 155;
a(3) = 1 + 4 + 9 + 16 + 25 + 49 + 64 = 168;
a(4) = 1 + 4 + 9 + 16 + 25 + 36 + 81 = 172;
a(5) = 1 + 4 + 9 + 16 + 36 + 49 + 64 = 179.
		

Programs

  • Haskell
    a224982 n = a224982_list !! (n-1)
    a224982_list = filter (p 7 $ tail a000290_list) [1..] where
       p k (q:qs) m = k == 0 && m == 0 ||
                      q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)
  • Mathematica
    nmax = 1000;
    S[n_] := S[n] = Union[Total /@ Subsets[
         Range[Floor[Sqrt[n]]]^2, {7}]][[1 ;; nmax]];
    S[nmax];
    S[n = nmax + 1];
    While[S[n] != S[n - 1], n++];
    S[n] (* Jean-François Alcover, Nov 20 2021 *)
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