A358180 Indices for A358168.

1, 30, 162, 1150, 11603, 104511, 1041245, 10226995, 101514698, 1008495923, 10060201866

Offset

1,2

Comments

a(6)-a(7) from Chuck Gaydos.

Links

Table of n, a(n) for n=1..11.

Mathematica

nn = 2^20; q[_] = False; q[0] = True; a[_] = 0; c[_] = -1; c[0] = 2; m = 1; {1}~Join~Reap[Do[j = c[m]; a[n] = m; c[m] = n; m = 0; If[j > 0, m = n - j]; If[! q[#2], Sow[n]; q[#2] = True] & @@ {a[n], IntegerLength[a[n]]}, {n, 3, nn}] ][[-1, -1]] (* Michael De Vlieger, Nov 05 2022 *)

Prog

(Python)
from itertools import count
def A358180(n):
    b, bdict, k = 0, {0:(1, )}, 10**(n-1) if n > 1 else 0
    for m in count(2):
        if b >= k:
            return m-1
        if len(l := bdict[b]) > 1:
            b = m-1-l[-2]
            if b in bdict:
                bdict[b] = (bdict[b][-1], m)
            else:
                bdict[b] = (m, )
        else:
            b = 0
            bdict[0] = (bdict[0][-1], m) # Chai Wah Wu, Nov 05 2022

Crossrefs

Cf. A181391, A358168.

Sequence in context: A064240 A141221 A159884 * A359025 A074357 A140594

Adjacent sequences: A358177 A358178 A358179 * A358181 A358182 A358183

Keyword

nonn,hard,more

Author

G. L. Honaker, Jr., Nov 02 2022

Extensions

a(8) from Michael De Vlieger, Nov 05 2022

a(9)-a(10) from Chai Wah Wu, Nov 05 2022

a(11) from Martin Ehrenstein, Nov 05 2022

Status

approved