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 1-3 of 3 results.

A294265 Number of partitions of n into squares that do not divide n.

Original entry on oeis.org

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 2, 1, 0, 0, 3, 1, 1, 0, 3, 3, 1, 0, 3, 3, 1, 0, 5, 3, 3, 0, 2, 3, 3, 0, 7, 3, 3, 3, 8, 1, 3, 0, 10, 9, 6, 0, 14, 9, 0, 0, 15, 12, 9, 4, 15, 16, 9, 0, 18, 18, 7, 1, 23, 18, 17, 0, 9, 22, 19, 5, 30, 28, 19, 5, 34, 6, 24, 2, 40, 36, 30
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 26 2017

Keywords

Examples

			a(25) = 2 because we have [16, 9] and [9, 4, 4, 4, 4].
		

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Product[1/(1 - Boole[Mod[n, k] > 0 && OddQ[DivisorSigma[0, k]]] x^k), {k, 1, n}], {x, 0, n}], {n, 0, 95}]

A300715 Number of compositions (ordered partitions) of n into squares that do not divide n.

Original entry on oeis.org

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 3, 0, 0, 7, 6, 0, 0, 14, 10, 4, 0, 22, 20, 10, 0, 32, 39, 20, 0, 49, 70, 42, 0, 12, 116, 88, 0, 128, 156, 174, 11, 207, 3, 320, 0, 333, 551, 575, 0, 555, 914, 0, 0, 959, 1502, 1829, 44, 1691, 2486, 3192, 0, 3000, 4172, 4005
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 11 2018

Keywords

Examples

			a(21) = 4 because we have [9, 4, 4, 4], [4, 9, 4, 4], [4, 4, 9, 4] and [4, 4, 4, 9].
		

Crossrefs

Programs

  • Maple
    a:= proc(m) option remember; local b; b:= proc(n) option
          remember; `if`(n=0, 1, add((s->`if`(s>n or irem(m, s)
           =0, 0, b(n-s)))(j^2), j=2..isqrt(n))) end; b(m)
        end:
    seq(a(n), n=0..100);  # Alois P. Heinz, Mar 11 2018
  • Mathematica
    Table[SeriesCoefficient[1/(1 - Sum[Boole[Mod[n, k] != 0 && IntegerQ[k^(1/2)]] x^k, {k, 1, n}]), {x, 0, n}], {n, 0, 75}]

A371968 Numbers k that are not the sum of distinct squares that do not divide k.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 30, 31, 32, 33, 35, 36, 37, 39, 40, 42, 43, 44, 46, 47, 48, 50, 51, 54, 55, 56, 57, 59, 60, 63, 64, 66, 67, 68, 71, 72, 75, 76, 79, 80, 82, 84, 88, 91, 92, 95, 96, 99, 104, 107, 108, 111, 112, 120, 124, 127, 128, 132, 135, 140, 144, 147, 148, 156, 160, 168, 172, 176, 184, 188, 192, 200, 216, 224, 252, 256, 288, 300, 432
Offset: 1

Views

Author

Robert Israel, Apr 15 2024

Keywords

Comments

Numbers k such that A294266(k) = 0.
No other terms <= 100000.

Examples

			a(20) = 21 is a term because the only way to write 21 as the sum of distinct squares is 1^2 + 2^2 + 4^2, but 21 is divisible by 1^2.
		

Crossrefs

Cf. A294266.

Programs

  • Maple
    filter:= proc(n) local P,k,x;
    P:= 1;
    for k from 2 to floor(sqrt(n)) do
      if n mod k^2 = 0 then next fi;
      P:= series(P*(1+x^(k^2)),x,n+1);
      if coeff(P,x,n) > 0 then return false fi;
    od;
    true
    end proc:
    select(filter, [$1..500]);

Extensions

More terms than usual in the DATA section, because these are probably all the terms.
Showing 1-3 of 3 results.