A071770 Tersum n + [n/3] (answer recorded in base 10).

0, 1, 2, 4, 5, 3, 8, 6, 7, 12, 13, 14, 16, 17, 15, 11, 9, 10, 24, 25, 26, 19, 20, 18, 23, 21, 22, 36, 37, 38, 40, 41, 39, 44, 42, 43, 48, 49, 50, 52, 53, 51, 47, 45, 46, 33, 34, 35, 28, 29, 27, 32, 30, 31, 72, 73, 74, 76, 77, 75, 80, 78, 79, 57, 58, 59, 61, 62, 60, 56, 54, 55, 69, 70

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..19682

P. Mathonet, M. Rigo, M. Stipulanti and N. Zénaïdi, On digital sequences associated with Pascal's triangle, arXiv:2201.06636 [math.NT], 2022.

Index entries for sequences that are permutations of the nonnegative integers

Formula

Tersum m + n: write m and n in base 3 and add mod 3 with no carries, e.g. 5 + 8 = "21" + "22" = "10" = 1. See A004482 for references.

Maple

a:= n-> (l-> add(irem(l[i]+l[i-1], 3)*3^(i-2),
         i=2..nops(l)))([convert(n, base, 3)[], 0]):
seq(a(n), n=0..73);  # Alois P. Heinz, Aug 07 2024

Prog

(PARI) a(n)={if(n==0, 0, fromdigits((digits(n, 3) + concat([0], digits(n\3, 3)))%3, 3))} \\ Andrew Howroyd, Aug 06 2024
(Python)
from sympy.ntheory import digits
def a(n):
    d = digits(n, 3)[1:]
    return int(str(d[0]) + "".join(str((d[i]+d[i-1])%3) for i in range(1, len(d))), 3)
print([a(n) for n in range(75)]) # Michael S. Branicky, Aug 07 2024

Crossrefs

Cf. A004482.

Inverse permutation to A370932.

Sequence in context: A099520 A327432 A159958 * A105529 A329454 A120237

Adjacent sequences: A071767 A071768 A071769 * A071771 A071772 A071773

Keyword

nonn,look,changed

Author

Paul D. Hanna, Jun 04 2002

Extensions

a(27) corrected by Sean A. Irvine, Aug 06 2024

Status

approved