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A164791
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a(n) is the smallest nonnegative number whose American English name has the letter "n" in the n-th position.
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9
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9, 1, 9, 20, 7, 11, 15, 13, 17, 47, 27, 77, 109, 120, 107, 111, 115, 113, 117, 147, 127, 177, 327, 377, 1120, 1107, 1111, 1115, 1113, 1117, 1147, 1127, 1177, 1327, 1377, 3327, 3377, 11377, 13327, 13377, 17377, 23327, 23377, 73377, 101377, 103327, 103377
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OFFSET
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1,1
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REFERENCES
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GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 70.
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LINKS
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EXAMPLE
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a(1)=9 ("Nine"), a(2)=1 ("oNe"), a(3)=9 ("niNe"), a(4)=20 ("tweNty").
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PROG
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(Python)
from num2words import num2words
from itertools import count, islice
def n2w(n):
return "".join(c for c in num2words(n).replace(" and", "") if c.isalpha())
def a(n):
return next(i for i in count(0) if len(w:=n2w(i))>=n and w[n-1]=="n")
(Python) # faster for initial segment of sequence; uses n2w, imports above
def agen(): # generator of terms
adict, n = dict(), 1
for i in count(0):
w = n2w(i)
if "n" in w:
locs = [i+1 for i, c in enumerate(w) if w[i] == "n"]
for v in locs:
if v not in adict: adict[v] = i
while n in adict: yield adict[n]; n += 1
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CROSSREFS
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KEYWORD
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nonn,word
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AUTHOR
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EXTENSIONS
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Definition clarified by N. J. A. Sloane, Apr 20 2023. We also need a British English analog of this, just as A362121 is an analog of A164790 (a(13) will be different).
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STATUS
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approved
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