A350562 For n >= 2, if there exists an m < n such that a(m) = a(n), take the largest such m and set a(n+1) = (n-m+1)*a(n); otherwise a(n+1) = 1. Start with a(1)=1 and a(2)=0.

1, 0, 1, 3, 1, 3, 9, 1, 4, 1, 3, 18, 1, 4, 24, 1, 4, 16, 1, 4, 16, 64, 1, 5, 1, 3, 48, 1, 4, 40, 1, 4, 16, 208, 1, 5, 65, 1, 4, 32, 1, 4, 16, 176, 1, 5, 55, 1, 4, 32, 352, 1, 5, 40, 1000, 1, 5, 25, 1, 4, 48, 1680, 1, 5, 40, 480, 1, 5, 25, 300, 1, 5, 25, 125, 1

Offset

1,4

Comments

A type of multiplicative Van Eck sequence.

Links

Table of n, a(n) for n=1..75.

Mathematica

f[1]=1; f[n_]:=0; f2[n_]:=0; a[n_]:=Block[{q=f2[x]}, If[q!=0, s[n]=((n-1-q)*(x))+x, s[n]=1]]; s[1]=1; s[2]=0; x=0; Do[x=a[n]; f2[x]=f[x]; f[x]=n, {n, 3, 100000}]; data=Table[s[n], {n, 1, 100000}]

Prog

(PARI) findm(list, n) = {forstep (m=n-1, 1, -1, if (list[m] == list[n], return(m))); return(0); }
lista(nn) = {my(list = List([1, 0])); for (n=3, nn, my(m=findm(list, n-1)); if (m, listput(list, (n-m)*list[n-1]), listput(list, 1)); ); Vec(list); } \\ Michel Marcus, Jan 17 2022
(Python)
from itertools import count, islice
def A350562_gen(): # generator of terms
    bdict = {1:1}
    yield 1
    b = 0
    for n in count(3):
        yield b
        c = (n-bdict[b])*b if b in bdict else 1
        bdict[b], b = n-1, c
A350562_list = list(islice(A350562_gen(), 30)) # Chai Wah Wu, Feb 11 2022

Crossrefs

Cf. A181391, A350228.

Sequence in context: A143453 A376499 A248830 * A164308 A082511 A265307

Adjacent sequences: A350559 A350560 A350561 * A350563 A350564 A350565

Keyword

nonn

Author

Jasmine Miller, Jan 05 2022

Status

approved