cp's OEIS Frontend

a(n) = product of primes whose indices are positions of nonzero-digits in factorial base representation of n (see A007623). Here positions are one-based, so that the least significant digit is the position 1, the next least significant the position 2, etc.

The square array A(row>=0, col>=0) is read by downwards antidiagonals as: A(0,0), A(0,1), A(1,0), A(0,2), A(1,1), A(2,0), A(0,3), A(1,2), A(2,1), A(3,0), ...

A(i,j) gives the rank of the permutation (in ordering used by table A060117) which is obtained by composing permutations p and q listed as the i-th and the j-th permutation in irregular table A060117 (note that the identity permutation is the 0th). Here the convention is that "permutations act of the left", thus, if p1 and p2 are permutations, then the product of p1 and p2 (p1 * p2) is defined such that (p1 * p2)(i) = p1(p2(i)) for i=1...

Equally, A(i,j) gives the rank in A060118 of the composition of the i-th and the j-th permutation in A060118, when convention is that "permutations act on the right".

Each row and column is a permutation of A001477, because this is the Cayley table ("multiplication table") of an infinite enumerable group, namely, that subgroup of the infinite symmetric group (S_inf) which consists of permutations moving only finite number of elements.

We say there is a "hit" in factorial base representation (A007623) of n when there is any such pair of nonzero digits d_i and d_j in positions i > j so that (i - d_i) = j. Here the rightmost (least significant digit) occurs at position 1. This sequence gives all "hit-free" numbers, meaning that for every nonzero digit d_i (in position i) in their factorial base representation the digit at the position (i - d_i) is 0.

Also numbers n for which A060502(n) = A060128(n), in other words, the numbers n for which the number of slopes in their factorial base representation (A007623) is equal to the number of non-singleton cycles of the permutation listed as n-th permutation in the list A060117 (or A060118).

This can be viewed as a factorial base analog of base-2 related A003714.

Equally: main diagonal of A261217.

For permutation p, which has rank n in permutation list A060117, a(n) gives the rank of the "square" of that permutation (obtained by composing it with itself as: q(i) = p(p(i))) in the same list. Equally, if permutation p has rank n in the order used in list A060118, a(n) gives the rank of the p*p in that same list. Thus zeros (which mark the identity permutation, with rank 0 in both orders) occur at positions where the permutations of A060117 (equally: of A060118) are involutions, listed by A261220.

Period 66. The sequence begins (from offset 0) with its lexicographically earliest rotation. Note the almost symmetric subsequence around the terms 66k and 66k+1: ...,16,12,12,9,8,8,9,10,12,16,... All integers in range [8,30] occur except 11, 17 and 29. The mean value of terms in the whole period of 66 is 17.7273.

This is the longest cyclic sequence that I have found so far (July 2010) on 8 X 8 toroidal grid, after the cycle of 48 given in A179409. Are there any longer cyclic sequences? A sequence to be computed: for n X n toroidal grid, the longest cycle of patterns that can occur. (Also other metrics for toroidal boards: how many patterns die in next generation, how many are stable, etc.)

Equally, for n>=1, each i in range [n!,(n+1)!-1] occurs n+1 times.

Used for computing A220659, A055089 and A060118: The n-th term a(n) tells which permutation (counted from the start, zero-based) of A055089 or A060117/A060118 the n-th term in those sequence belongs to.

The term a(n) gives the position (zero-based, starting from the left hand end of permutation) of a corresponding permutation A055089 and A060117/A060118 from which the term A055089(n) or A060118(n) is to be picked.

Equally, column 1 of A261217.

Take the n-th (n>=0) permutation from the list A060117, change 1 to 2 and 2 to 1 to get another permutation, and note its rank in the same list to obtain a(n).

Equally, we can take the n-th (n>=0) permutation from the list A060118, swap the elements in its two leftmost positions, and note the rank of that permutation in A060118 to obtain a(n).

Self-inverse permutation of nonnegative integers.

a(n) gives the distance of the rightmost zero from the right hand end of factorial base representation of n (A007623), particularly, 1 when n is even, and 0 for those cases when there are no nonleading zeros present (terms of A227157).

Sequence starts from n=1, to avoid ambiguities with case zero.

These are indices of derangements in permutation lists A060117 & A060118 when only elements in range [1..(1+A084558(n))] are considered to be a part of the finite permutation whose rank number is n.