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A354521
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a(n) is the position of the first letter in the US English name of n that can also be found in the English name of n+1.
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0
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2, 1, 1, 3, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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OFFSET
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0,1
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COMMENTS
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Spaces and punctuation are ignored when determining the position of the letter.
a(n) is well-defined as n and n+1 always share a letter (see formulas). - Michael S. Branicky, Aug 20 2022
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LINKS
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FORMULA
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For n > 1000, a(n) = 1 unless n = b + 1000^e - 1 (for e >= 1, 1 <= b <= 999) in which case a(n) = a(b). Subsequently, 1 <= a(n) <= 3. - Michael S. Branicky, Aug 20 2022
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EXAMPLE
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For n = 4, a(4) = 1 since the 1st letter of 'four' can also be found in 'five'.
For n = 59, a(59) = 2 since the 2nd letter of 'fifty-nine' can be found in 'sixty'.
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PROG
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(Python)
from num2words import num2words as n2w
def a(i):
w1 = n2w(i).replace(' ', '').replace('-', '')
w2 = n2w(i+1).replace(' ', '').replace('-', '')
for j in range(len(w1)):
if w1[j] in w2:
return j+1
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CROSSREFS
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KEYWORD
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nonn,easy,word
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AUTHOR
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STATUS
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approved
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