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A261902 Irregular triangle read by rows: T(n,m) = number of permutations of {1, 2, ..., n} which form arithmetic progressions modulo m (n>=1, 1<=m<=n+2). 0
1, 1, 1, 2, 2, 2, 2, 6, 2, 6, 2, 2, 24, 8, 4, 8, 4, 2, 120, 12, 8, 4, 20, 2, 2, 720, 72, 48, 8, 8, 12, 6, 2, 5040, 144, 48, 16, 8, 4, 42, 4, 2, 40320, 1152, 144, 128, 16, 8, 12, 23, 6, 2, 362880, 2880, 1296, 96, 64, 16, 8, 8, 54, 4, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

REFERENCES

F. Luca, A. O. Munagi, The Number Of Permutations Which Form Arithmetic Progressions Modulo m, Annals of the Alexandru Ioan Cuza University, 2014, DOI: 10.2478/aicu-2014-0053

LINKS

Table of n, a(n) for n=1..63.

EXAMPLE

Triangle begins:

1,1,1,

2,2,2,2,

6,2,6,2,2,

24,8,4,8,4,2,

120,12,8,4,20,2,2,

720,72,48,8,8,12,6,2,

5040,144,48,16,8,4,42,4,2,

40320,1152,144,128,16,8,12,23,6,2,

362880,2880,1296,96,64,16,8,8,54,4,2,

...

CROSSREFS

T(n,n) = A002618(n).

Sequence in context: A198889 A130754 A164126 * A163368 A151948 A080400

Adjacent sequences:  A261899 A261900 A261901 * A261903 A261904 A261905

KEYWORD

nonn,tabf

AUTHOR

N. J. A. Sloane, Sep 07 2015

STATUS

approved

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Last modified March 20 23:22 EDT 2019. Contains 321354 sequences. (Running on oeis4.)