The Carmichael function is defined recursively by the following formulas:
If $p_1,\ldots,p_n$ are distinct primes, then $ \lambda(p_1^{k_1} \cdots p_n^{k_n}) \;=\; \text{lcm}\bigl(\lambda(p_1^{k_1}),\ldots,\lambda(p_n^{k_n})\bigr) $
If $p$ is an odd prime and $k\geq 1$, then $\lambda(p^k) = p^{k-1}(p-1)$.
$\lambda(2) = 1$, $\lambda(4) = 2$, and $\lambda(2^k) = 2^{k-2}$ for $k \geq 3$.
Since $\lambda(p^k)$ is even for any prime power $p^k$ other than $2$, the values Carmichael function are always even except for $\lambda(1) = \lambda(2) = 1$.
Moreover, if $p$ is an odd prime and $p \mid \lambda(n)$, then either:
$(p-1) \mid \lambda(n)$, or
$p \mid (q-1)$ and $(q-1) \mid \lambda(n)$ for some prime $q$.
This places severe restrictions on the values of the Carmichael function. In particular, if $p$ is an odd prime and $2p+1$ is not prime, then $2p$ is not a possible value of the Carmichael function. Thus, the numbers $\{14,26,34,38,\ldots\}$ do not arise as values of the Carmichael function.
Note that this list is not exhaustive. For example, $68$ is not a value of the Carmichael function, though it is not of the form I have indicated.