Progressions

N-th member of arithmetical progression
a_n = a1 + d (n - 1)

Members of of an arithmetical progression and arithmetic average
a_n = (a_M1 + a_P1) / 2

Sum of the members of an arithmetic progression (arithmetic series)
S_n = (2 * a_1 + d (n-1)) * n / 2

Sum of the members of an arithmetic progression (arithmetic series)
S_n = ( a_1 + a_n) * n / 2

N-th member of geometric progression
b_n = b1*q^(n-1)

Members of geometric progression and geometric average
b_n = saknis(b_M1 * b_P1)

Sum of the members of geometric progression (geometric series)
S_n = b1 * (q^n - 1) / (q - 1)

Sum of the members of geometric progression (geometric series)
S_n = (b_n *q - b1) / (q - 1)

Sum of an infinite geometric progression (infinite geometric series)
S_n = b1 / (1 - q)