A175728 Decimal expansion of e written as a sequence of distinct positive integers.

2, 7, 1, 8, 28, 18, 284, 5, 90, 4, 52, 3, 53, 60, 287, 47, 13, 526, 6, 24, 9, 77, 57, 2470, 93, 69, 99, 59, 574, 96, 696, 76, 27, 72, 40, 766, 30, 35, 354, 75, 94, 571, 38, 21, 78, 525, 16, 64, 274, 2746, 63, 91, 93200, 305, 992, 181, 74, 135, 966, 290, 43, 572, 900, 33, 42

Offset: 1

Author

Jason G. Wurtzel, Aug 19 2010

Keywords

• nonn
• base

Comments

Inverse: 3, 1, 12, 10, 8, 19, 2, 4, 21, 119, 86, 166, 17, 154, 160, 47, 192, 6, 83, 214, ..., . - Robert G. Wilson v, Aug 22 2010

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001113, A064809.

Programs

Mathematica

rd = RealDigits[E, 10, 200][[1]]; lst = {}; f[n_] := Block[{k = 1}, While[a = FromDigits[ Take[ rd, k]]; MemberQ[lst, a] || rd[[k + 1]] == 0, k++ ]; AppendTo[ lst, a]; rd = Drop[rd, k]]; Array[f, 70]; lst (* Robert G. Wilson v, Aug 22 2010 *)

Python

from itertools import islice
from sympy import exp
def diggen():
    yield from map(int, str(exp(1).n(10**5))[:-1].replace(".", ""))
def agen(): # generator of terms
    g = diggen()
    aset, nextd = set(), next(g)
    while True:
        an, nextd = nextd, next(g)
        while an in aset or nextd == 0:
            an, nextd = int(str(an) + str(nextd)), next(g)
        yield an
        aset.add(an)
print(list(islice(agen(), 65))) # Michael S. Branicky, Mar 31 2022

Extensions

More terms from Robert G. Wilson v, Aug 22 2010