A Disappearing Number, Barbican, LondonBlack Eyed Susan, Theatre Royal, Bury St EdmundsAwake and Sing!, Almeida, London

The mathematics of longing, love and loss

A blackboard stands centre stage in A Disappearing Number, Complicite's intriguing new piece about mathematics and mourning. At one point, creating an eerie image of generations dying and then haunting the living, the blackboard starts spinning and a stream of people stride through this revolving wall into the darkness beyond. At the same time, they keep ethereally reappearing, for the blackboard has transformed into a translucent screen. Their shadows are cast back from the other side.

The show is, essentially, a multilayered experimental biodrama that defies linear time, splicing together a modern-day tragic love story with a portrait of the historic friendship between the Cambridge don, G H Hardy, and the virtually self-taught Indian genius, Srinivasa Ramanujan. The latter died in 1920, aged only 32 but his mathematical formulae foreshadowed today's all-connecting string theory.

Turning high-powered numerical equations into theatre was never going to be easy. Characteristically, however, director Simon McBurney begins with a winning comical routine. The teasing joke is that any non-geniuses in the audience are lost within minutes and laughing about it while Saskia Reeves's Ruth – an eager bespectacled lecturer and Ramanujan expert – enthuses about the thrilling beauty of maths' so-called infinite series.

Reeves is hilarious yet entrancing as she scribbles never-ending sums on the board, and she is soon in a budding relationship with an American-Asian globetrotting business man, Firdous Bamji's Al, who works in the futures market and emerges from the audience to ask for her phone number. He will later be bereaved and symbolically locked in this lecture hall through a long dark night, with only memories and a suitcase of Ruth's belongings.

Not everything works out in this production. The interlocking of maths and music (with a score by Nitin Sawhney) is engrossing. Tabla drumming and chanted tihis are used to express the infinite series rapidly forming inside Ramanujan's head, though not all the multimedia moments are so brilliant. Ramanujan's story is glimpsed in fragments which raise some unanswered questions, and more ideas are introduced than McBurney's cast have, perhaps, had time to fully develop in the devising process. Nonetheless daringly ambitious and frequently inspired, they are exploring numerous themes here, including Asian and Western culture, infinity and mortality, loss and what lasts, the gulfs between people and, most touchingly, our manifold means of communication (from planes and phones to the meeting of minds across centuries).

By contrast, Black Eyed Susan marks a return to a vintage theatrics. Bury St Edmunds' intimate Theatre Royal has just been exquisitely restored to its former Regency glory by artistic director Colin Blumenau and the National Trust. With its picturesque, blue, sky-and-clouds ceiling and refreshingly simple wooden balconies, this is an architectural treasure. Whether Blumenau's revival of Douglas Jerrold's early 19th-century nautical drama matches up is another question. This romp about a wicked landlord, a bluff sailor and his pretty, virtuous wife is not far off a panto. Still, with its satire of avaricious capitalism and its folk songs and shanties, this is a curiosity, hovering between Dickens, John Gay and Gilbert and Sullivan.

Meanwhile, the Almeida Theatre continues to rediscover forgotten foreign gems with Clifford Odets' Jewish domestic drama, Awake and Sing! In the Depression-stricken Bronx of the 1930s, a frustrated 20-something, Ralph (Ben Turner), yearns to realise his émigré grandfather's Marxist ideals but is kept under the thumb of his thoroughly capitalist, domineering mother (Stockard Channing). This piece does get preachy towards the end but, before that, it weaves beautifully big politico-economic issues into everyday domesticity – observed with a Chekhovian eye for detail. Apart from a few wobbly accents, Michael Attenborough's ensemble are superb with Nigel Lindsay as the sneering but ultimately decent wide-boy, Moe, and with Channing's petty, pragmatic obsession with money growing subtly monstrous. Recommended.

'A Disappearing Number' (0845 120 7550) to 6 October; 'Black Eyed Susan' (01284 769505) to 22 September; 'Awake and Sing!' (020 7359 4404) to 20 October

Further reading 'A Mathematician's Apology' by GH Hardy (CUP)