A101634 Subtract 1, multiply by 1, subtract 2, multiply by 2, etc.

6, 5, 6, 9, 20, 75, 414, 2849, 22728, 204471, 2044610, 22490589, 269886924, 3508529843, 49119417606, 736791263865, 11788660221584, 200407223766639, 3607330027799178, 68539270528184021, 1370785410563680020

Offset: 1

Author

Zak Seidov, Jan 26 2005

Keywords

• easy
• nonn

Comments

Inspired by A019460. a(1) = 6 is the least integer producing all nonnegative terms.

Crossrefs

Cf. A019460.

Programs

Mathematica

a=6;bb={a};Do[b=i(a-i);a=b;bb={bb, a}, {i, 20}];Flatten[bb]

Formula

Recurrence: a(1) = 6; a(n+1) = n*a(n) - n^2. [Edited by Georg Fischer, Dec 28 2021]