A077384 a(1) = 1, then add, multiply, subtract, multiply 2, 3, 4, 5; 6, 7, 8, 9; ... in that order.

1, 3, 9, 5, 25, 31, 217, 209, 1881, 1891, 20801, 20789, 270257, 270271, 4054065, 4054049, 68918833, 68918851, 1309458169, 1309458149, 27498621129, 27498621151, 632468286473, 632468286449, 15811707161225, 15811707161251

Offset

1,2

Links

Table of n, a(n) for n=1..26.

Formula

a(1) = 1, a(2n+1) = (2n+1)*a(2n), a(4n) = a(4n-1)-4n, a(4n+2) = a(4n+1) + 4n+2.

Mathematica

FoldList[If[Mod[#2, 4]==2, #1+#2, If[Mod[#2, 4]==3, #1*#2, If[Mod[#2, 4] ==0, #1-#2, #1*#2]]]&, 1, Range[2, 26]] (* James C. McMahon, Oct 09 2023 *)

Prog

(Python)
from itertools import count, islice
def A077384_gen(): # generator of terms
    yield (a:=1)
    for n in count(2, 4):
        yield (a:=a+n)
        yield (a:=a*(n+1))
        yield (a:=a-n-2)
        yield (a:=a*(n+3))
A077384_list = list(islice(A077384_gen(), 20)) # Chai Wah Wu, Apr 19 2023

Crossrefs

Other operation orders: A077382, A077383, A362269, A362270, A362271, A362272.

Sequence in context: A103934 A365203 A186814 * A122943 A276148 A182946

Adjacent sequences: A077381 A077382 A077383 * A077385 A077386 A077387

Keyword

nonn

Author

Amarnath Murthy, Nov 06 2002

Extensions

More terms from Sascha Kurz, Jan 04 2003

Status

approved