A347208 - OEIS

A347208

Number of permutations of [n] that are in the same position in A030298 as they are in A098281.

1, 2, 3, 3, 3, 10, 5, 4, 5, 13, 3, 6, 5

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

For n = 7 the a(7) = 5 permutations are 1234567, 1234576, 1236745, 6574231, 7654321, which are in positions 1, 2, 17, 4198, 5040 respectively in both sequences A030298 and A098281.

MATHEMATICA

perms[n_] := perms[n] = If[n == 1, {{1}}, Flatten[Table[Insert[#, n, pos], {pos, -1, -n, -1}]& /@ perms[n-1], 1]];

a[n_] := Count[Transpose@{perms[n], Permutations[Range[n]]}, {p_, p_}];

Table[a[n], {n, 1, 10}] (* Jean-François Alcover, Sep 02 2021 *)

CROSSREFS

Cf. A030298, A098281.

Sequence in context: A334579 A199457 A361378 * A210483 A022296 A013069

Adjacent sequences: A347205 A347206 A347207 * A347209 A347210 A347211

KEYWORD

nonn,more

AUTHOR

William Chang, Aug 23 2021

STATUS

approved