1, 1, 3, 15, 105
OEIS: A001147
Formula: ZZ(2*n-3).multifactorial(2)
Serie: 1 - sqrt(1-2*x)
Equation: (P-1)**2 - (1-2*x)
Actions: s[1], s[2], s[2, 1] + s[3], s[2, 1, 1] + 2*s[2, 2] + 2*s[3, 1] + 2*s[4], s[2, 1, 1, 1] + 4*s[2, 2, 1] + 4*s[3, 1, 1] + 6*s[3, 2] + 6*s[4, 1] + 3*s[5], s[2, 1, 1, 1, 1] + 6*s[2, 2, 1, 1] + 7*s[2, 2, 2] + 7*s[3, 1, 1, 1] + 21*s[3, 2, 1] + 8*s[3, 3] + 14*s[4, 1, 1] + 21*s[4, 2] + 14*s[5, 1] + 6*s[6]