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A138077 Index of the largest maximal subgroup of PSL(3,q) as q runs through the prime powers (A000961). 3
7, 13, 21, 31, 57, 73, 91, 133, 183, 273, 307, 381, 553, 651, 757, 871, 993 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Warning: entries need checking!

First eight entries agree with the ATLAS. Rest not checked. - Eric M. Schmidt, Apr 21 2013

From Ed Pegg Jr, May 16 2019: (Start)

(n^2+n+1,n+1) difference sets exist when n is a prime power.

(7,3), (1,2,4)

(13,4), (0,1,3,9)

(21,5), (3,6,7,12,14)

(31,6), (1,5,11,24,25,27)

(57,8), (0,1,6,15,22,26,45,55)

(73,9), (0,1,12,20,26,30,33,35,57)

(91,10), (0,2,6,7,18,21,31,54,63,71)

(133,12), (1,10,11,13,27,31,68,75,83,110,115,121)

(183,14), (1,13,20,21,23,44,61,72,77,86,90,116,122,169) (End)

LINKS

Table of n, a(n) for n=1..17.

Dan Gordon, Difference Sets

MATHEMATICA

First /@ Select[Table[{n^2 + n + 1, n + 1}, {n, 2, 50}],

  Length[FactorInteger[#[[2]] - 1]] == 1 &]

CROSSREFS

Cf. A000961, A003807 (order of PSL(3,q)), A335865.

Sequence in context: A013652 A099988 A076947 * A288655 A124192 A335277

Adjacent sequences:  A138074 A138075 A138076 * A138078 A138079 A138080

KEYWORD

nonn,more

AUTHOR

John Cannon and N. J. A. Sloane, Dec 06 2009

EXTENSIONS

a(3) corrected by Eric M. Schmidt, Apr 20 2013

STATUS

approved

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Last modified June 21 00:06 EDT 2021. Contains 345319 sequences. (Running on oeis4.)