Kummer confluent hypergeometric function 1F1(a; b; z).
Hypergeometric1F1[a, b, z]
Hypergeometric1F1[1, 2, 3.0]
→ 6.3618456410625575Plot[Hypergeometric1F1[1, 2, x], {x, -5, 5}]
→ -Graphics-Series[Hypergeometric1F1[a, b, x], {x, 0, 3}]
→ SeriesData[x, 0, {1, a/b, (a*(1 + a))/(2*(1 + b)*b), (a*(1 + a)*(2 + a))/(6*(1 + b)*(2 + b)*b)}, 0, 4, 1]