# [R], 36 bytes

<!-- language-all: lang-r -->

    function(W,u=unique(W))any(u-seq(u))

[Try it online!][TIO-kyngsqns]

[R]: https://www.r-project.org/
[TIO-kyngsqns]: https://tio.run/##dY@7DsIwDEV3PqNTLNEVwdAPYEfqnCcND4ekMVB@PhTRpZIzWFeyj@XjVFxXHKHOPqDot9QR@khW9AASJ0HtaKMggOIEZbc/hSNm0cgG2sMONuum5NtKKh5XWlcW9FxmSR7Rxrrz4C/X2x3DI6Yx0/P1nj7Dgq95XoC9rmRFShmer5lUxNP8lPnFf1y@ "R – Try It Online"

Takes input as a vector of integers from `1` to `26`. Outputs `FALSE` for truthy and `TRUE` for falsey.