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A077383

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

1, 3, 9, 5, 10, 60, 53, 61, 549, 539, 550, 6600, 6587, 6601, 99015, 98999, 99016, 1782288, 1782269, 1782289, 37428069, 37428047, 37428070, 898273680, 898273655, 898273681, 24253389387, 24253389359, 24253389388, 727601681640, 727601681609

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..31.

EXAMPLE

a(2) = a(1) + 2 = 3, a(3) = 3*3 = 9, a(4) = 9 - 4 = 5, a(5) = 5 + 5 = 10, etc.

MAPLE

a := proc(n) if n=1 then 1 elif n mod 3 = 2 then a(n-1)+n elif n mod 3 = 0 then n*a(n-1) elif n mod 3 = 1 then a(n-1)-n else fi end: # Emeric Deutsch, Dec 17 2003

MATHEMATICA

FoldList[If[Mod[#2, 3]==2, #1+#2, If[Mod[#2, 3]==0, #1*#2, #1-#2]]&, 1, Range[2, 31]] (* James C. McMahon, Oct 10 2023 *)

PROG

(Python)

from itertools import count, islice

def A077383_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)

A077383_list = list(islice(A077383_gen(), 20)) # Chai Wah Wu, Apr 19 2023