A220692 Square array A220691 transposed.

0, 1, 0, 3, 0, 0, 6, 1, 1, 0, 10, 2, 1, 0, 0, 15, 4, 2, 1, 0, 0, 21, 6, 4, 1, 1, 0, 0, 28, 9, 5, 2, 2, 0, 0, 0, 36, 12, 7, 3, 2, 1, 0, 0, 0, 45, 16, 10, 5, 3, 2, 1, 0, 0, 0, 55, 20, 12, 6, 4, 2, 2, 0, 0, 0, 0, 66, 25, 15, 8, 6, 3, 3, 1, 0, 0, 0, 0

Offset

1,4

Links

Table of n, a(n) for n=1..78.

Index entries for sequences related to subset sums modulo m

Formula

a(n) = A220691bi(A004736(n),A002260(n)). (As a sequence. As an array this is the transpose of the square array given in A220691).

Mathematica

a[n_, 1] := n*(n-1)/2; a[n_, k_] := Module[{r}, r = Reduce[1 <= i < j <= n && Mod[i+j, k] == 0, {i, j}, Integers]; Which[Head[r] === Or, Length[r], Head[r] === And, 1, r === False, 0, True, Print[r, " not parsed"]]]; Table[a[n-k+1, k], {n, 1, 13} , {k, 1, n}] // Flatten (* Jean-François Alcover, Mar 04 2014 *)

Prog

(Scheme): (define (A220692 n) (A220691bi (A004736 n) (A002260 n)))

Crossrefs

Cf. A220691, A220693, A061857.

Sequence in context: A145225 A332442 A061480 * A048962 A135028 A325006

Adjacent sequences: A220689 A220690 A220691 * A220693 A220694 A220695

Keyword

nonn,tabl

Author

Antti Karttunen, Feb 18 2013

Status

approved