cp's OEIS Frontend

A354521 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.

%I A354521 #47 Oct 01 2022 19:44:40
%S A354521 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,
%T A354521 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,
%U A354521 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
%N A354521 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.
%C A354521 Spaces and punctuation are ignored when determining the position of the letter.
%C A354521 a(n) is well-defined as n and n+1 always share a letter (see formulas). - _Michael S. Branicky_, Aug 20 2022
%F A354521 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
%e A354521 For n = 4, a(4) = 1 since the 1st letter of 'four' can also be found in 'five'.
%e A354521 For n = 59, a(59) = 2 since the 2nd letter of 'fifty-nine' can be found in 'sixty'.
%o A354521 (Python)
%o A354521 from num2words import num2words as n2w
%o A354521 def a(i):
%o A354521     w1 = n2w(i).replace(' ','').replace('-','')
%o A354521     w2 = n2w(i+1).replace(' ','').replace('-','')
%o A354521     for j in range(len(w1)):
%o A354521         if w1[j] in w2:
%o A354521             return j+1
%K A354521 nonn,easy,word
%O A354521 0,1
%A A354521 _Ray G. Opao_, Aug 16 2022