A350217 a(1) = 1; a(n) > a(n-1) is the smallest number whose name in English does not contain the first letter of the name of a(n-1).

1, 3, 4, 6, 8, 30, 100, 300, 400, 600, 800, 2000, 1000000

Offset

1,2

Links

Table of n, a(n) for n=1..13.

Mathematica

name[n_]:=IntegerName[n, "Words"]; a[1]=1; a[n_]:=a[n]=Module[{i=a[n-1]+1}, While[
StringContainsQ[name[i], StringTake[name[a[n-1]], 1]], i++ ]; i]; a/@Range[12]

Prog

(Python)
from num2words import num2words
def n2w(n): return num2words(n).replace(" and", "")
def afind(limit):
    alst, aset = [1], {1}
    print(1, end=", ")
    while alst[-1] < limit:
        an = alst[-1] + 1
        avoid = n2w(alst[-1])[0]
        while an in aset or avoid in n2w(an): an += 1
        alst.append(an); aset.add(an)
        print(an, end=", ")
afind(100000) # Michael S. Branicky, Dec 20 2021

Crossrefs

Cf. A350218, A277971, A277972.

Sequence in context: A063506 A084438 A186700 * A028987 A284615 A186709

Adjacent sequences: A350214 A350215 A350216 * A350218 A350219 A350220

Keyword

nonn,word,fini,full

Author

Ivan N. Ianakiev, Dec 20 2021

Status

approved