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 1-2 of 2 results.

A147706 Number of partitions of n into parts having distinct digital roots (A010888).

Original entry on oeis.org

1, 1, 2, 2, 3, 4, 5, 6, 8, 10, 11, 15, 16, 20, 25, 28, 32, 39, 46, 50, 62, 66, 78, 93, 101, 112, 132, 150, 161, 192, 202, 232, 268, 287, 312, 361, 400, 425, 497, 516, 582, 658, 698, 748, 858, 932, 982, 1135, 1164, 1296, 1443, 1519, 1610, 1845, 1968, 2059, 2360, 2395
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 11 2008

Keywords

Comments

a(n) <= A000009(n).
Likely a duplicate of A114098. [From R. J. Mathar, Dec 13 2008]

Examples

			A000009(16) = 32, in which the following 4 partitions
contain parts with common digital roots:
12 + 3 + 1, 11 + 3 + 2, 10 + 5 + 1 and 10 + 3 + 2 + 1,
therefore a(16) = 32 - 4 = 28.
		

Crossrefs

A114091 Number of partitions of n into parts that are distinct mod 3.

Original entry on oeis.org

1, 1, 2, 2, 2, 4, 3, 3, 7, 4, 4, 11, 5, 5, 16, 6, 6, 22, 7, 7, 29, 8, 8, 37, 9, 9, 46, 10, 10, 56, 11, 11, 67, 12, 12, 79, 13, 13, 92, 14, 14, 106, 15, 15, 121, 16, 16, 137, 17, 17, 154, 18, 18, 172, 19, 19, 191, 20, 20, 211, 21, 21, 232, 22, 22, 254, 23, 23, 277, 24
Offset: 1

Views

Author

Giovanni Resta, Feb 06 2006

Keywords

Comments

Each partition can have at most three parts if n is a multiple of three and at most two parts otherwise. - Andrew Howroyd, Jan 28 2020
In general, these sequences can be generated by a linear recurrence with a signature that contains k=1..d tuples of the form (d-1 zeros, (-1)^(k-1) * binomial(d, k)), where d = number of distinct parts (here: d=3). - Georg Fischer, Sep 03 2022

Examples

			a(5)=2 because there are 2 such partition of 5: {5}, {2,3}.
		

Crossrefs

Cf. A008619(d=2), A114092(4), A114093(5), A114094(6), A114095(7), A114096(8), A114098(9), A114097(10).

Programs

  • Mathematica
    << DiscreteMath`Combinatorica`; np[n_]:= Length@Select[Mod[ #,3]& /@ Partitions[n],(Length@# != Length@Union@#)&]; lst = Array[np,50] (* or *)
    LinearRecurrence[{0, 0, 3, 0, 0, -3, 0, 0, 1}, {1, 1, 2, 2, 2, 4, 3, 3, 7}, 64] (* Georg Fischer, Sep 03 2022 *)
  • PARI
    a(n)={1 + n\3 + if(n%3==0, binomial(n/3,2))} \\ Andrew Howroyd, Jan 28 2020

Formula

a(3*n) = 1 + n + binomial(n, 2); a(3*n-1) = a(3*n-2) = n. - Andrew Howroyd, Jan 28 2020

Extensions

Terms a(51) and beyond from Andrew Howroyd, Jan 28 2020
Showing 1-2 of 2 results.