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.

A144324 Square array A(n,k), n>=1, k>=1, read by antidiagonals, with A(1,k)=1 and sequence a_k of column k shifts left when Dirichlet convolution (DC:(b,b)->a) applied k times.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 4, 4, 1, 1, 8, 16, 9, 1, 1, 16, 64, 70, 18, 1, 1, 32, 256, 540, 280, 40, 1, 1, 64, 1024, 4216, 4320, 1168, 80, 1, 1, 128, 4096, 33264, 67456, 35008, 4672, 168, 1, 1, 256, 16384, 264160, 1064448, 1083136, 280064, 18884, 340, 1, 1, 512, 65536
Offset: 1

Views

Author

Alois P. Heinz, Sep 17 2008

Keywords

Examples

			Square array begins:
  1,  1,   1,    1,     1, ...
  1,  1,   1,    1,     1, ...
  2,  4,   8,   16,    32, ...
  4, 16,  64,  256,  1024, ...
  9, 70, 540, 4216, 33264, ...
		

Crossrefs

Rows 1+2, 3-4 give: A000012, A000079(k+1), A000302(k+1).

Programs

  • Maple
    with(numtheory): dc:= proc(b,c) proc(n) option remember; add(b(d) *c(n/d), d=`if`(n<0,{},divisors(n))) end end: A:= proc(n, k) local a, b, t; b[1]:= dc(a,a); for t from 2 to k do b[t]:= dc(b[t-1],b[t-1]) od: a:= n-> `if`(n=1, 1, b[k](n-1)); a(n) end: seq(seq(A(n, 1+d-n), n=1..d), d=1..11);
  • Mathematica
    dc[b_, c_] := Module[{proc}, proc[n_] := proc[n] = Sum [b[d] *c[n/d], {d, If[n < 0, {}, Divisors[n]]}]; proc]; A [n_, k_] := Module[{a, b, t}, b[1] = dc[a, a]; For[t = 2, t <= k, t++, b[t] = dc[b[t-1], b[t-1]]]; a = Function[m, If[m == 1, 1, b[k][m-1]]]; a[n]]; Table[Table[A[n, 1+d-n], {n, 1, d}], {d, 1, 11}] // Flatten (* Jean-François Alcover, Dec 20 2013, translated from Maple *)

A144823 Square array A(n,k), n>=1, k>=1, read by antidiagonals, with A(1,k)=1 and sequence a_k of column k shifts left when Dirichlet convolution with a_k (DC:(b,a_k)->a) applied k times.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 3, 4, 1, 1, 4, 9, 9, 1, 1, 5, 16, 30, 18, 1, 1, 6, 25, 70, 90, 40, 1, 1, 7, 36, 135, 280, 288, 80, 1, 1, 8, 49, 231, 675, 1168, 864, 168, 1, 1, 9, 64, 364, 1386, 3475, 4672, 2647, 340, 1, 1, 10, 81, 540, 2548, 8496, 17375, 18884, 7968, 698, 1, 1, 11, 100
Offset: 1

Views

Author

Alois P. Heinz, Sep 21 2008

Keywords

Examples

			Square array A(n,k) begins:
   1,   1,    1,     1,     1,      1,      1,      1, ...
   1,   1,    1,     1,     1,      1,      1,      1, ...
   2,   3,    4,     5,     6,      7,      8,      9, ...
   4,   9,   16,    25,    36,     49,     64,     81, ...
   9,  30,   70,   135,   231,    364,    540,    765, ...
  18,  90,  280,   675,  1386,   2548,   4320,   6885, ...
  40, 288, 1168,  3475,  8496,  18130,  35008,  62613, ...
  80, 864, 4672, 17375, 50976, 126910, 280064, 563517, ...
		

Crossrefs

Rows 1+2, 3-4 give: A000012, A000027, A000290, A002414.

Programs

  • Maple
    with(numtheory): dc:= proc(b,c) proc(n) option remember; add(b(d) *c(n/d), d=`if`(n<0,{},divisors(n))) end end: A:= proc(n, k) local a, b, t; b[1]:= dc(a,a); for t from 2 to k do b[t]:= dc(b[t-1],a) od: a:= n-> `if`(n=1, 1, b[k](n-1)); a(n) end: seq(seq(A(n, 1+d-n), n=1..d), d=1..12);
  • Mathematica
    dc[b_, c_] := Module[{proc}, proc[n_] := proc[n] = Sum [b[d] *c[n/d], {d, If[n < 0, {}, Divisors[n]]}]; proc]; A [n_, k_] := Module[{a, b, t}, b[1] = dc[a, a]; For[t = 2, t <= k, t++, b[t] = dc[b[t-1], a]]; a = Function[m, If[m == 1, 1, b[k][m-1]]]; a[n]]; Table[Table [A[n, 1+d-n], {n, 1, d}], {d, 1, 12}] // Flatten (* Jean-François Alcover, Dec 20 2013, translated from Maple *)
Showing 1-2 of 2 results.