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

1,2

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: A225163 A319540 A190634 * A347908 A227403 A156736

Adjacent sequences: A130418 A130419 A130420 * A130422 A130423 A130424

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