A130421 Numbers k such that 4^k == 2 (mod k).

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

Author

Jon E. Schoenfield, May 26 2007

Keywords

• nonn

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)

Crossrefs

Cf. A006935 (odd terms times 2), A130422, A347906 (odd terms), A347908 (even terms).

Programs

Mathematica

Join[{1,2},Select[Range[107000000],PowerMod[4,#,#]==2&]] (* Harvey P. Dale, Jun 13 2013 *)

Extensions

Terms a(28) onward from Max Alekseyev, Jun 18 2014

b-file corrected by Max Alekseyev, Oct 09 2016