Do I bother pursuing this friendship?

I'm a first year Uni student and over the past five months or so I've been getting friendly with a group of second year students in the same society. We go to the same social event every week, once or twice we've met up outside of society events too and occasionally I've been round theirs to drink. We also go on the same society trips regularly, on which I usually end up spending most of my time chatting to them. We have common experiences and interests, and I've also been able to speak to each of them individually and get on well.

I really enjoy spending time with them, however, the crux of the problem is that I often feel left out of their plans. Usually I have to be the organiser or ask specifically about their plans to be included. This is naturally quite draining and demoralising. Perhaps they only see me as a society friend, or perhaps the fact I'm only first year - even though we're all the same age so I wouldn't have thought that matters. Realistically I think it's because they've known each other for longer.

Considering this friendship dynamic and how I feel like it's me putting all the effort in, I'm beginning to wonder whether I should bother pursuing this friendship or if it would benefit me better focusing my attention elsewhere. Especially coming up to six months now which I've known them. Is it a good idea to communicate with them that I'd be interested in spending more time with them, or would that come across too pushy? I wanted to share this to splurge my thoughts and hear outside opinions on this matter.