A339567 Numbers k such that A007088(k) == 1 (mod k).
1, 5, 15, 25, 55, 91, 137, 525, 625, 925, 3967, 5995, 7625, 10767, 25087, 57225, 68817, 565027, 591415, 2515825, 2757625, 4162019, 5276309, 96689255, 115686005, 133890625, 242899421, 492029715, 588620625, 1839399055, 7786281065, 11231388063, 17251448809, 71050380625
Offset: 1
Examples
a(3) = 15 is a term because 15 = 1111_2 and 1111 == 1 (mod 15).
Programs
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Maple
filter:= t -> convert(t,binary) mod t = 1: filter(1):= true: select(filter, [seq(i,i=1..10^7,2)]);
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Mathematica
Block[{a = {1}, k}, Do[If[Mod[FromDigits@ IntegerDigits[i, 2], i] == 1, AppendTo[a, i]], {i, 2, 10^7}]; a] (* Michael De Vlieger, Dec 12 2020 *) -
PARI
isok(n) = Mod(fromdigits(binary(n)), n) == 1; forstep(k=1, 10^7, 2, if(isok(k), print1(k, ", "))); \\ Daniel Suteu, Dec 12 2020
Extensions
a(30)-a(34) from Daniel Suteu, Dec 12 2020
Comments