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A140539 a(n) is smallest number with divisors which are congruent to 1, 2, ..., n-1 mod n. 1
1, 1, 2, 6, 8, 30, 12, 60, 96, 270, 90, 420, 72, 1638, 840, 1080, 300, 4410, 432, 5940, 3360, 6930, 540, 10920, 2880, 19890, 9360, 27300, 1680, 43890, 1200, 36720, 84480, 151470, 97440, 107100, 3780, 139650, 120120, 83160, 4800, 395850, 5040, 318780, 191520, 217350 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Andrew Weimholt, Table of n, a(n) for n = 1..125

EXAMPLE

a(7)=12: 12's divisors are 1,2,3,4,6,12 and

1 == 1 mod 7

2 == 2 mod 7

3 == 3 mod 7

4 == 4 mod 7

12 == 5 mod 7

6 == 6 mod 7

PROG

(PARI) a(n) = {if (n == 1, return (1)); if (n == 2, return (1)); i = 2; cref = Set(vector(n-1, k, k)); while (1, cong = Set(); fordiv (i, d, if (d % n, cong = setunion(cong, Set(d % n))); ); if (cong == cref, return (i)); i++; ); } \\ Michel Marcus, Mar 08 2013

CROSSREFS

Sequence in context: A290423 A272614 A210737 * A056188 A020696 A290249

Adjacent sequences:  A140536 A140537 A140538 * A140540 A140541 A140542

KEYWORD

nonn

AUTHOR

Andrew Weimholt, Jul 04 2008

STATUS

approved

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Last modified August 22 10:37 EDT 2017. Contains 290946 sequences.