A376849 Numbers k such that psi(k + psi(k)) = psi(k) + psi(psi(k)), where psi = A002322.

2, 5, 10, 34, 80, 111, 196, 204, 222, 328, 351, 646, 654, 704, 837, 876, 935, 943, 969, 1053, 1100, 1140, 1220, 1224, 1372, 1408, 1526, 1824, 1864, 2368, 2496, 2511, 2715, 2816, 2842, 3159, 3294, 3528, 3648, 3672, 4332, 4473, 4600, 4736, 4992, 5500, 5632, 6325, 6528, 7296, 7412, 7512, 7533, 7832, 7959

Offset: 1

Author

Robert Israel, Oct 06 2024

Keywords

• nonn

Examples

			a(3) = 10 is a term because psi(10) = 4, psi(4) = 2, and psi(10 + 4) = psi(14) = 6 = 4 + 2.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002322, A376830, A376831, A376843, A376844, A376848, A376851.

Programs

Maple

filter:= proc(k) uses numtheory; local s;
 s:= lambda(k);
 lambda(k+s) = s + lambda(s)
end proc:
select(filter, [$1..10000]);

Mathematica

Select[Range[8000], CarmichaelLambda[ #+CarmichaelLambda[#]] == CarmichaelLambda[#]+CarmichaelLambda[CarmichaelLambda[#]] &] (* Stefano Spezia, Oct 07 2024 *)