A330347 a(1)=1, a(2)=2; for n > 2, a(n) = (sum0 * sum1) mod n, where sum0 is the sum of all previous even terms, sum1 is the sum of all previous odd terms.

1, 2, 2, 0, 4, 2, 3, 0, 4, 6, 3, 8, 1, 0, 14, 0, 13, 0, 8, 10, 0, 6, 6, 0, 12, 22, 12, 14, 17, 6, 5, 14, 2, 26, 5, 0, 19, 14, 11, 12, 37, 2, 12, 0, 10, 0, 36, 14, 7, 10, 37, 38, 0, 42, 35, 44, 3, 10, 43, 0, 12, 46, 12, 32, 10, 6, 33, 66, 39, 66, 57, 18, 67, 14, 16, 0

Offset

1,2

Links

Table of n, a(n) for n=1..76.

Mathematica

f[s_] := Join[s, {Mod[Total @ Select[s, EvenQ] * Total @ Select[s, OddQ], Length[s] + 1]}]; Nest[f, {1, 2}, 100] (* Amiram Eldar, Mar 01 2020 *)

Prog

(Python)
a = [1, 2]
s0 = 2
s1 = 1
for n in range(3, 1000):
    v = s0 * s1 % n
    a.append(v)
    if v&1:  s1 += v
    else:    s0 += v
print(a)

Crossrefs

Cf. A332581, A329681.

Sequence in context: A218869 A144458 A098268 * A329681 A276275 A128585

Adjacent sequences: A330344 A330345 A330346 * A330348 A330349 A330350

Keyword

nonn,easy

Author

Alex Ratushnyak, Feb 29 2020

Status

approved