A227911 Number of remainders occurring only once when dividing n by 1,2,...n.

1, 0, 1, 1, 1, 2, 2, 2, 3, 2, 2, 4, 4, 4, 5, 4, 4, 5, 5, 6, 7, 6, 6, 7, 7, 6, 7, 7, 7, 9, 9, 9, 10, 9, 9, 10, 10, 10, 11, 10, 10, 12, 12, 13, 14, 13, 13, 14, 14, 13, 14, 14, 14, 15, 15, 15, 16, 15, 15, 17, 17, 17, 18, 17, 17, 18, 18, 19, 20, 19, 19, 20, 20, 20, 21, 21, 21, 22, 22, 22, 23, 22, 22, 24, 24, 23

Offset

1,6

Comments

Number of 1's in row n of A072528.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

9 divided by 1,2...9 gives the remainders 0,1,0,1,4,3,2,1,0 of which 2,3,4 occur only once, so a(9)=3.

Mathematica

Table[Count[Tally[Mod[n, Range[n]]], _?(#[[2]]==1&)], {n, 90}] (* Harvey P. Dale, Aug 17 2023 *)

Prog

(PARI) a(n)=v=vector(n+1); for(d=1, n, t=(n%d)+1; v[t]=v[t]+1); sum(i=1, n, v[i]==1)

Crossrefs

Sequence in context: A290978 A142240 A284565 * A325783 A048288 A050677

Adjacent sequences: A227908 A227909 A227910 * A227912 A227913 A227914

Keyword

nonn

Author

Ralf Stephan, Oct 13 2013

Status

approved