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A130421
Numbers k such that 4^k == 2 (mod k).
11
1, 2, 14, 1022, 20066, 80519, 107663, 485918, 1284113, 1510313, 2531678, 3677198, 3933023, 4557713, 8277458, 8893262, 21122318, 24849833, 26358638, 39852014, 42448478, 71871113, 76712318, 80646143, 98058097, 104832833, 106694033, 131492498, 144322478, 146987033, 164360606, 168204191, 175126478, 176647378, 188997463, 196705598
OFFSET
1,2
COMMENTS
Some terms above 10^15: 26435035805519327, 158975398896178078, 64044049390757098943, 1063423126446412987081943, 1091220919655042176978844783, 81074850280355100090334498663, 6317483763950169936179578094903, 5672799393875320397186007124651847, 170923900137537174138295268515194974, 195746953975871672436191077726091399305155458, 325665752547333314939363628501536024940097079718953, 953533053776414279913696071891872697927468471633033, 85791212788381063775490416118630897060666265030605503, 334519297382630382793758729321508383611586565722054114034741260213364710519401967713. - Max Alekseyev, Jun 18 2014
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..2617 (all terms below 10^15)
MATHEMATICA
Join[{1, 2}, Select[Range[107000000], PowerMod[4, #, #]==2&]] (* Harvey P. Dale, Jun 13 2013 *)
CROSSREFS
Cf. A006935 (odd terms times 2), A130422, A347906 (odd terms), A347908 (even terms).
Sequence in context: A319540 A190634 A376057 * A347908 A227403 A156736
KEYWORD
nonn
AUTHOR
Jon E. Schoenfield, May 26 2007
EXTENSIONS
Terms a(28) onward from Max Alekseyev, Jun 18 2014
b-file corrected by Max Alekseyev, Oct 09 2016
STATUS
approved