A362272 a(1) = 1, then multiply, subtract, and add 2, 3, 4; 5, 6, 7; ... in that order.

1, 2, -1, 3, 15, 9, 16, 128, 119, 129, 1419, 1407, 1420, 19880, 19865, 19881, 337977, 337959, 337978, 6759560, 6759539, 6759561, 155469903, 155469879, 155469904, 4042217504, 4042217477, 4042217505, 117224307645, 117224307615, 117224307646, 3751177844672, 3751177844639

Offset

1,2

Links

Table of n, a(n) for n=1..33.

Formula

a(1)=1; for n > 1,

a(n) = a(n-1) * n if n mod 3 = 2,

a(n-1) - n if n mod 3 = 0,

a(n-1) + n if n mod 3 = 1.

Example

a(2) = 1 * 2 = 2;
a(3) = 2 - 3 = -1;
a(4) = -1 + 4 = 3.

Mathematica

FoldList[If[Mod[#2, 3]==2, #1*#2, If[Mod[#2, 3]==0, #1-#2, #1+#2]]&, 1, Range[2, 33]] (* James C. McMahon, Oct 09 2023 *)

Prog

(Python)
from itertools import count, islice
def A362272_gen(): # generator of terms
    yield (a:=1)
    for n in count(2, 3):
        yield (a:=a*n)
        yield (a:=a-n-1)
        yield (a:=a+n+2)
A362272_list = list(islice(A362272_gen(), 20)) # Chai Wah Wu, Apr 19 2023

Crossrefs

Other operation orders: A077382, A077383, A362269, A362270, A362271.

Sequence in context: A366591 A007447 A153189 * A095852 A283748 A209365

Adjacent sequences: A362269 A362270 A362271 * A362273 A362274 A362275

Keyword

sign

Author

James C. McMahon, Apr 19 2023

Status

approved