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 11-17 of 17 results.

A342250 Number of ways to write n as an ordered sum of seven powers of 2.

Original entry on oeis.org

1, 7, 21, 42, 77, 126, 168, 218, 294, 357, 427, 546, 637, 672, 756, 840, 854, 966, 1134, 1218, 1302, 1408, 1484, 1554, 1680, 1827, 1995, 2002, 1925, 2016, 1988, 1904, 2142, 2352, 2282, 2352, 2534, 2520, 2604, 2954, 3080, 3276, 3262, 3234, 3150, 3248, 3164, 3402, 3640
Offset: 7

Views

Author

Ilya Gutkovskiy, Mar 07 2021

Keywords

Crossrefs

Programs

  • Maple
    N:= 100:
    S:= add(x^(2^j),j=0..ilog2(N-6))^7:
    [seq](coeff(S,x,j),j=7..N); # Robert Israel, Feb 26 2023
  • Mathematica
    nmax = 55; CoefficientList[Series[Sum[x^(2^k), {k, 0, Floor[Log[2, nmax]] + 1}]^7, {x, 0, nmax}], x] // Drop[#, 7] &

Formula

G.f.: ( Sum_{k>=0} x^(2^k) )^7.

A342251 Number of ways to write n as an ordered sum of eight powers of 2.

Original entry on oeis.org

1, 8, 28, 64, 126, 224, 336, 464, 645, 840, 1044, 1344, 1666, 1904, 2192, 2528, 2730, 3024, 3528, 3920, 4284, 4768, 5168, 5488, 5965, 6552, 7140, 7616, 7834, 8176, 8400, 8352, 8862, 9632, 9800, 10080, 10788, 10976, 11152, 12208, 13090, 13664, 14392, 14672, 14868, 15008, 15344
Offset: 8

Views

Author

Ilya Gutkovskiy, Mar 07 2021

Keywords

Crossrefs

Programs

  • Maple
    N:= 100:
    S:= add(x^(2^j),j=0..ilog2(N-7))^8:
    seq(coeff(S,x,j),j=8..N); # Robert Israel, Feb 26 2023
  • Mathematica
    nmax = 54; CoefficientList[Series[Sum[x^(2^k), {k, 0, Floor[Log[2, nmax]] + 1}]^8, {x, 0, nmax}], x] // Drop[#, 8] &

Formula

G.f.: ( Sum_{k>=0} x^(2^k) )^8.

A342252 Number of ways to write n as an ordered sum of nine powers of 2.

Original entry on oeis.org

1, 9, 36, 93, 198, 378, 624, 927, 1341, 1849, 2412, 3159, 4074, 4950, 5904, 7032, 8010, 9018, 10488, 11970, 13356, 15108, 16848, 18315, 20085, 22257, 24444, 26671, 28674, 30510, 32208, 33282, 34974, 37590, 39384, 40986, 43668, 45468, 46512, 49620, 53298, 55890, 59304, 62442
Offset: 9

Views

Author

Ilya Gutkovskiy, Mar 07 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 52; CoefficientList[Series[Sum[x^(2^k), {k, 0, Floor[Log[2, nmax]] + 1}]^9, {x, 0, nmax}], x] // Drop[#, 9] &

Formula

G.f.: ( Sum_{k>=0} x^(2^k) )^9.

A342254 Number of ways to write n as an ordered sum of ten powers of 2.

Original entry on oeis.org

1, 10, 45, 130, 300, 612, 1095, 1750, 2655, 3850, 5281, 7110, 9460, 12060, 14940, 18352, 21850, 25380, 29790, 34740, 39672, 45480, 51885, 57870, 64375, 72090, 80145, 88630, 97660, 106380, 114736, 122260, 130050, 139740, 148990, 157572, 168240, 178200, 185490, 196200, 210082
Offset: 10

Views

Author

Ilya Gutkovskiy, Mar 07 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Sum[x^(2^k), {k, 0, Floor[Log[2, nmax]] + 1}]^10, {x, 0, nmax}], x] // Drop[#, 10] &

Formula

G.f.: ( Sum_{k>=0} x^(2^k) )^10.

A159981 Catalan numbers read modulo 4.

Original entry on oeis.org

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

Views

Author

Philippe Deléham, Apr 28 2009

Keywords

Comments

Essentially the same as A073267. - R. J. Mathar, May 25 2009

Crossrefs

Programs

Formula

a(n) = A000108(n) mod 4.
Asymptotic mean: lim_{n->oo} (1/n) Sum_{k=1..n} a(k) = 0 (Burns, 2016). - Amiram Eldar, Jan 26 2021

Extensions

Extended by R. J. Mathar, Apr 30 2009

A281228 Expansion of (Sum_{k>=0} x^(3^k))^2 [even terms only].

Original entry on oeis.org

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

Views

Author

Ilya Gutkovskiy, Jan 18 2017

Keywords

Comments

Number of ways to write 2n as an ordered sum of two powers of 3.
First bisection of self-convolution of characteristic function of powers of 3.

Examples

			G.f. = x^2 + 2*x^4 + x^6 + 2*x^10 + 2*x^12 + x^18 + 2*x^28 + 2*x^30 + 2*x^36 + ...
a(2) = 2 because we have [3, 1] and [1, 3].
		

Crossrefs

Programs

  • Mathematica
    Take[CoefficientList[Series[Sum[x^3^k, {k, 0, 15}]^2, {x, 0, 260}], x], {1, -1, 2}]

Formula

G.f.: (Sum_{k>=0} x^(3^k))^2 [even terms only].

A289682 Catalan numbers read modulo 16.

Original entry on oeis.org

1, 1, 2, 5, 14, 10, 4, 13, 6, 14, 12, 2, 12, 4, 8, 13, 6, 6, 12, 6, 4, 12, 8, 2, 12, 12, 8, 4, 8, 8, 0, 13, 6, 6, 12, 14, 4, 12, 8, 6, 4, 4, 8, 12, 8, 8, 0, 2, 12, 12, 8, 12, 8, 8, 0, 4, 8, 8, 0, 8, 0, 0, 0, 13, 6, 6, 12, 14, 4, 12, 8, 14, 4, 4, 8, 12, 8, 8, 0, 6, 4, 4, 8, 4, 8, 8, 0, 12
Offset: 0

Views

Author

R. J. Mathar, Jul 09 2017

Keywords

Comments

Conjecture: a(2^n-1) = 13 and a(2^n) = 6 for n >= 3. - Robert Israel, Jul 09 2017

Crossrefs

Cf. A000108, A036987 (mod 2), A073267 (mod 4), A159987 (mod 8).
Cf. A048881 (2-adic valuation of A000108).

Programs

  • Magma
    [Catalan(n) mod 16: n in [0..100]]; // Vincenzo Librandi, Jul 10 2017
  • Maple
    seq ( modp(A000108(n),16),n=0..120) ;
  • Mathematica
    Table[Mod[CatalanNumber[n], 16], {n, 0, 100}] (* Vincenzo Librandi, Jul 10 2017 *)
  • PARI
    a(n) = (binomial(2*n, n)/(n+1)) % 16; \\ Michel Marcus, Jul 09 2017
    

Formula

a(n) = A000108(n) mod 16.
Asymptotic mean: lim_{n->oo} (1/n) Sum_{k=1..n} a(k) = 0 (Burns, 2016). - Amiram Eldar, Jan 26 2021
Previous Showing 11-17 of 17 results.