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.

Previous Showing 61-68 of 68 results.

A140150 a(1)=1, a(n)=a(n-1)+n^2 if n odd, a(n)=a(n-1)+ n^4 if n is even.

Original entry on oeis.org

1, 17, 26, 282, 307, 1603, 1652, 5748, 5829, 15829, 15950, 36686, 36855, 75271, 75496, 141032, 141321, 246297, 246658, 406658, 407099, 641355, 641884, 973660, 974285, 1431261, 1431990, 2046646, 2047487, 2857487, 2858448, 3907024, 3908113
Offset: 1

Views

Author

Artur Jasinski, May 12 2008

Keywords

Crossrefs

Programs

  • Mathematica
    a = {}; r = 2; s = 4; Do[k = 0; Do[k = k + (Sin[Pi m/2]^2) m^r + (Cos[Pi m/2]^2) m^s, {m, 1, n}]; AppendTo[a, k], {n, 1, 100}]; a (*Artur Jasinski*)
    nxt[{n_,a_}]:={n+1,If[EvenQ[n],a+(n+1)^2,a+(n+1)^4]}; NestList[nxt,{1,1},40][[All,2]] (* or *) LinearRecurrence[{1,5,-5,-10,10,10,-10,-5,5,1,-1},{1,17,26,282,307,1603,1652,5748,5829,15829,15950},40] (* Harvey P. Dale, Aug 28 2017 *)

Formula

G.f.: x*(1+16*x+4*x^2+176*x^3-10*x^4+176*x^5+4*x^6+16*x^7+x^8)/((1+x)^5*(x-1)^6). [From R. J. Mathar, Feb 22 2009]

A140152 a(1)=1, a(n)=a(n-1)+n^3 if n odd, a(n)=a(n-1)+ n^0 if n is even.

Original entry on oeis.org

1, 2, 29, 30, 155, 156, 499, 500, 1229, 1230, 2561, 2562, 4759, 4760, 8135, 8136, 13049, 13050, 19909, 19910, 29171, 29172, 41339, 41340, 56965, 56966, 76649, 76650, 101039, 101040, 130831, 130832, 166769, 166770, 209645, 209646, 260299
Offset: 1

Views

Author

Artur Jasinski, May 12 2008

Keywords

Crossrefs

Programs

  • Mathematica
    a = {}; r = 3; s = 0; Do[k = 0; Do[k = k + (Sin[Pi m/2]^2) m^r + (Cos[Pi m/2]^2) m^s, {m, 1, n}]; AppendTo[a, k], {n, 1, 100}]; a (*Artur Jasinski*)
    nxt[{a_,b_}]:={a+1,If[EvenQ[a],b+(a+1)^3,b+1]}; Transpose[NestList[nxt,{1,1},40]][[2]] (* Harvey P. Dale, Dec 13 2011 *)

Formula

a(n) = a(n-1)+4*a(n-2)-4*a(n-3)-6*a(n-4)+6*a(n-5)+4*a(n-6)-4*a(n-7)-a(n-8)+a(n-9). G.f.: x*(-1-x-23*x^2+3*x^3-23*x^4-3*x^5-x^6+x^7)/((1+x)^4*(x-1)^5). [R. J. Mathar, Feb 22 2009]

A202107 a(n) = n^4*(n+1)^4/8.

Original entry on oeis.org

2, 162, 2592, 20000, 101250, 388962, 1229312, 3359232, 8201250, 18301250, 37949472, 74030112, 137149922, 243101250, 414720000, 684204032, 1095962562, 1710072162, 2606420000, 3889620000, 5694792642, 8194304162, 11605565952, 16200000000, 22313281250, 30356972802
Offset: 1

Views

Author

Martin Renner, Dec 11 2011

Keywords

Comments

A relation between fourth powers and the sum of fifth and seventh powers. See the first formula, which is from Beiler.

References

  • Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966, p. 161.

Crossrefs

Programs

Formula

a(n) = 2*(Sum_{k=1..n} k)^4 = Sum_{k=1..n} (k^5 + k^7).
a(n) = 2*A059977(n-1).
a(n) = A000539(n) + A000541(n).
G.f.: -2*x*(1+72*x+603*x^2+1168*x^3+603*x^4+72*x^5+x^6) / (x-1)^9. - R. J. Mathar, Dec 13 2011
a(n) = 2*(A000217(n)^4). - Zak Seidov, Jan 21 2012
From Amiram Eldar, Apr 09 2024: (Start)
Sum_{n>=1} 1/a(n) = 8*Pi^4/45 + 80*Pi^2/3 - 280.
Sum_{n>=1} (-1)^(n+1)/a(n) = 280 - 320*log(2) - 48*zeta(3). (End)

A263689 a(n) = (2*n^6 - 6*n^5 + 5*n^4 - n^2 + 12)/12.

Original entry on oeis.org

1, 1, 2, 34, 277, 1301, 4426, 12202, 29009, 61777, 120826, 220826, 381877, 630709, 1002002, 1539826, 2299201, 3347777, 4767634, 6657202, 9133301, 12333301, 16417402, 21571034, 28007377, 35970001, 45735626, 57617002, 71965909, 89176277, 109687426, 133987426, 162616577, 196171009, 235306402, 280741826
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 20 2015

Keywords

Examples

			a(0) = 1,
a(1) = 0^5 + 1 = 1,
a(2) = 1^5 + 1 = 2,
a(3) = 2^5 + 2 = 34,
a(4) = 3^5 + 34 = 227,
a(5) = 4^5 + 227 = 1301, etc.
		

Crossrefs

Programs

  • Mathematica
    Table[(1/12) (12 + (-1 + n)^2 n^2 (-1 + 2 (-1 + n) n)), {n, 0, 35}]
  • PARI
    first(m)=vector(m,n,n--;(2*n^6 - 6*n^5 + 5*n^4 - n^2 + 12)/12) \\ Anders Hellström, Nov 20 2015

Formula

G.f.: (1 - 6*x + 16*x^2 + 6*x^3 + 81*x^4 + 20*x^5 + 2*x^6)/(1 - x)^7.
a(n + 1) = a(n) + n^5, a(0) = 1.
a(n + 1) - a(n) = A000584(n).
a(n + 1) = A000539(n) + 1.
Sum_{n>0} 1/(a(n + 1) - a(n)) = zeta(5) = 1.036927755...

A265021 Sum of fifth powers of the first n even numbers.

Original entry on oeis.org

0, 32, 1056, 8832, 41600, 141600, 390432, 928256, 1976832, 3866400, 7066400, 12220032, 20182656, 32064032, 49274400, 73574400, 107128832, 152564256, 213030432, 292265600, 394665600, 525356832, 690273056, 896236032, 1151040000, 1463540000, 1843744032
Offset: 0

Views

Author

Assoul Abdelkarim, Nov 30 2015

Keywords

Examples

			a(4) =  2^5 + 4^5 + 6^5 + 8^5 = 41600.
		

Crossrefs

Cf. A000539, A002594 (the same for odd numbers).

Programs

  • Magma
    [(8/3)*n^2*(n+1)^2*(2*n^2+2*n-1): n in [0..30]]; // Vincenzo Librandi, Dec 01 2015
    
  • Mathematica
    Accumulate[Range[0, 60, 2]^5] (* Michael De Vlieger, Nov 30 2015 *)
    CoefficientList[Series[32 x (1 + 26 x + 66 x^2 + 26 x^3 + x^4)/(1 - x)^7, {x, 0, 33}], x] (* Vincenzo Librandi, Dec 01 2015 *)
  • PARI
    vector(100, n, n--; (8/3)*n^2*(n+1)^2*(2*n^2+2*n-1)) \\ Altug Alkan, Dec 01 2015

Formula

a(n) = 32 * Sum_{i=0..n} i^5 = (8/3)*n^2*(n+1)^2*(2*n^2+2*n-1).
a(n) = 32 * A000539(n).
G.f.: 32*x*(1 + 26*x + 66*x^2 + 26*x^3 + x^4)/(1-x)^7. - Vincenzo Librandi, Dec 01 2015
a(n) = 7*a(n-1)-21*a(n-2)+35*a(n-3)-35*a(n-4)+21*a(n-5)-7*a(n-6)+a(n-7). - Vincenzo Librandi, Dec 01 2015

A351770 a(n) = Sum_{j=1..n} Sum_{i=1..j} (i*j)^5.

Original entry on oeis.org

0, 1, 1057, 68125, 1399325, 15227450, 110102426, 597639882, 2621915850, 9756511275, 31839011275, 93340522951, 250280856007, 622316813300, 1450471654100, 3196426654100, 6706824221076, 13476181309557, 26055415288725, 48670370285425, 88136930285425, 155187254126926
Offset: 0

Views

Author

Roudy El Haddad, Feb 18 2022

Keywords

Comments

a(n) is the sum of all products of two elements from the set {1^5, ..., n^5}.

Crossrefs

Cf. A001296 (for power 1), A060493 (for squares), A346642 (for cubes), A351766 (for fourth powers).
Cf. A000584 (fifth powers), A000539 (sum of fifth powers).

Programs

  • Maple
    seq(n*(n+1)*(n+2)*(44*n^9+276*n^8+492*n^7-48*n^6-609*n^5+207*n^4+487*n^3-291*n^2-90*n+60)/3168,
    n=0..30);# Robert Israel, Feb 18 2022
  • PARI
    {a(n) = n*(n+1)*(n+2)*(44*n^9+276*n^8+492*n^7-48*n^6-609*n^5+207*n^4+487*n^3-291*n^2-90*n+60)/3168};
    
  • PARI
    a(n) = sum(j=1, n, sum(i=1, j, i^5*j^5));

Formula

a(n) = n*(n+1)*(n+2)*(44*n^9 + 276*n^8 + 492*n^7 - 48*n^6 - 609*n^5 + 207*n^4 + 487*n^3 - 291*n^2 - 90*n + 60)/3168.
G.f.: x*(1 + 1044*x + 54462*x^2 + 595860*x^3 + 2048388*x^4 + 2563644*x^5 + 1193226*x^6 + 188508*x^7 + 7635*x^8 + 32*x^9)/(1-x)^13. - Robert Israel, Feb 18 2022

A351805 a(n) = Sum_{1 <= i < j <= n} j^5*i^5.

Original entry on oeis.org

0, 0, 32, 8051, 290675, 4353175, 38761975, 243824182, 1194358326, 4842169350, 16924669350, 52488756425, 147511725257, 381689190701, 920589376525, 2089893985900, 4500779925100, 9254143113132, 18262909865676, 34746798604575, 63973358604575, 114343801467875
Offset: 0

Views

Author

Roudy El Haddad, Feb 19 2022

Keywords

Comments

a(n) is the sum of all products of two distinct elements from the set {1^5, ..., n^5}.

Crossrefs

Cf. A000217 (for power 0), A000914 (for power 1), A000596 (for squares), A347107 (for cubes), (for fourth powers).
Cf. A000584 (fifth powers), A000539 (sum of fifth powers).

Programs

  • PARI
    {a(n) = n*(n-1)*(n+1)*(44*n^9+120*n^8-132*n^7-540*n^6+99*n^5+912*n^4-11*n^3-672*n^2+120)/3168};

Formula

a(n) = Sum_{j=2..n} Sum_{i=1..j-1} j^5*i^5.
a(n) = n*(n - 1)*(n + 1)*(44*n^9 + 120*n^8 - 132*n^7 - 540*n^6 + 99*n^5 + 912*n^4 - 11*n^3 - 672*n^2 + 120)/3168.
G.f.: -x^2*(x^9 +1044*x^8 +54462*x^7 +595860*x^6 +2048388*x^5 +2563644*x^4 +1193226*x^3 +188508*x^2 +7635*x +32)/(x-1)^13. - Alois P. Heinz, Feb 19 2022

A362946 Positive integers that cannot be expressed as 1^e_1 + 2^e_2 + 3^e_3 ... + k^e_k with each exponent positive.

Original entry on oeis.org

2, 4, 7, 11, 13, 19, 25, 31
Offset: 1

Views

Author

Robert C. Lyons, Jul 05 2023

Keywords

Comments

I conjecture that this list is finite.

Examples

			1 is not in the sequence because it's equal to 1^1.
3 is not in the sequence because it's equal to 1^1 + 2^1.
20 is not in the sequence because it's equal to 1^1 + 2^4 + 3^1.
29 is not in the sequence because it's equal to 1^1 + 2^2 + 3^1 + 4^2 + 5^1.
		

Crossrefs

Programs

  • Python
    from itertools import product
    import math
    max_term = 250
    seq_set = set(range(1, max_term+1))
    # Use the quadratic formula to calculate the maximum value for k,
    # such that 1^1 + 2^1 + 3^1 + ... + k^1 is less than max_term.
    max_k = int((-1 + math.sqrt(1 + 8 * max_term))/2.0) + 1
    for k in range(1, max_k+1):
        list_of_exponent_ranges = [range(1,2)]
        for i in range(2, k+1):
            max_exponent = int(math.log(max_term, i))
            list_of_exponent_ranges.append(range(1, max_exponent+1))
        for exponents in product(*list_of_exponent_ranges):
            total = 0
            for i in range(1, k+1):
                total += int(i**exponents[i-1])
                if total > max_term:
                    total = 0
                    break
            if total in seq_set:
                seq_set.remove(total)
    print(sorted(seq_set))
Previous Showing 61-68 of 68 results.