A133903 a(n) = a(n-1) + A000005(n-1) if a(n-1) is not divisible by 3, otherwise a(n) = a(n-1)/3.

1, 2, 4, 6, 2, 4, 8, 10, 14, 17, 21, 7, 13, 15, 5, 9, 3, 1, 7, 9, 3, 1, 5, 7, 15, 5, 9, 3, 1, 3, 1, 3, 1, 5, 9, 3, 1, 3, 1, 5, 13, 15, 5, 7, 13, 19, 23, 25, 35, 38, 44, 48, 16, 18, 6, 2, 10, 14, 18, 6, 2, 4, 8, 14, 21, 7, 15, 5, 11, 15, 5, 7, 19, 21, 7, 13, 19, 23

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Mathematica

Nest[Append[#1, If[Divisible[Last[#1], 3], Last[#1]/3, Last[#1] + DivisorSigma[0, #2]]] & @@ {#, Length[#]} &, {1}, 77] (* Michael De Vlieger, Mar 21 2022 *)

Prog

(PARI) lista(nn) = {my(va = vector(nn)); va[1] = 1; for (n=2, nn, va[n] = if (va[n-1] % 3, va[n-1] + numdiv(n-1), va[n-1]/3); ); va; } \\ Michel Marcus, Nov 28 2020

Crossrefs

Cf. A000005 (number of divisors).

Sequence in context: A050975 A053446 A354577 * A278263 A236188 A352599

Adjacent sequences: A133900 A133901 A133902 * A133904 A133905 A133906

Keyword

easy,nonn

Author

Ctibor O. Zizka, Jan 07 2008

Extensions

Corrected and extended by Michel Marcus, Nov 28 2020

Status

approved