A base station apparatus comprising: an information generating section arranged to generate resource allocation information indicating a plurality of resources to be allocated to a terminal apparatus, in an uplink; and a transmission section arranged to transmit the resource allocation information to the terminal apparatus wherein each cluster of resources in the plurality of resources includes one or more contiguous resource block groups, RBGs,wherein the clusters are separated from each other in a frequency domain; the resource allocation information includes a combinatorial index, r, that is calculated by using: a notification start RBG index, s, for each of the clusters, where the notification start RBG index coincides with an allocation start RBG index s' for the respective cluster; a notification end RBG index, e, for each of the clusters, the notification end RBG index e being obtained by adding 1 to an allocation end RBG index e' for the respective cluster, the notification end RBG index thereby being an index of an RBG next to the respective cluster; M, being a number of the clusters; and a value of N' that is obtained based on a number of RBGs, N, included in a system bandwidth in the uplink, so that r = ∑ i = 0 2 ⁢ M − 1 〈 N ′ − b i 2 ⁢ M − i 〉, r ∈ 0,..., N ′ 2 ⁢ M − 1, wherein 〈 x y 〉 = { x y = C x y x ≥ y 0 x < y, i is an index of the respective cluster and b i takes values { s 0, e 0, s 1, e 1,..., s M-1, e M-1}, wherein N' is set to equal N, unless lo g 2 N 2 ⁢ M < lo g 2 N + 1 2 ⁢ M holds true, in which case N' is set to N+1 instead. an information generating section arranged to generate resource allocation information indicating a plurality of resources to be allocated to a terminal apparatus, in an uplink; and a transmission section arranged to transmit the resource allocation information to the terminal apparatus wherein each cluster of resources in the plurality of resources includes one or more contiguous resource block groups, RBGs,wherein the clusters are separated from each other in a frequency domain; the resource allocation information includes a combinatorial index, r, that is calculated by using: a notification start RBG index, s, for each of the clusters, where the notification start RBG index coincides with an allocation start RBG index s' for the respective cluster; a notification end RBG index, e, for each of the clusters, the notification end RBG index e being obtained by adding 1 to an allocation end RBG index e' for the respective cluster, the notification end RBG index thereby being an index of an RBG next to the respective cluster; M, being a number of the clusters; and a value of N' that is obtained based on a number of RBGs, N, included in a system bandwidth in the uplink, a notification start RBG index, s, for each of the clusters, where the notification start RBG index coincides with an allocation start RBG index s' for the respective cluster; a notification end RBG index, e, for each of the clusters, the notification end RBG index e being obtained by adding 1 to an allocation end RBG index e' for the respective cluster, the notification end RBG index thereby being an index of an RBG next to the respective cluster; M, being a number of the clusters; and a value of N' that is obtained based on a number of RBGs, N, included in a system bandwidth in the uplink, so that r = ∑ i = 0 2 ⁢ M − 1 〈 N ′ − b i 2 ⁢ M − i 〉, r ∈ 0,..., N ′ 2 ⁢ M − 1, wherein 〈 x y 〉 = { x y = C x y x ≥ y 0 x < y, i is an index of the respective cluster and b i takes values { s 0, e 0, s 1, e 1,..., s M-1, e M-1}, wherein N' is set to equal N, unless lo g 2 N 2 ⁢ M < lo g 2 N + 1 2 ⁢ M holds true, in which case N' is set to N+1 instead.