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A375507 a(1) = 1. For n > 1; a(n) is equal to a(n-1) plus the decimal value of the concatenation of the first n-1 digits of the sequence.

%I A375507 #23 Aug 20 2024 16:06:01
%S A375507 1,2,14,135,1349,13490,134903,1349038,13490389,134903902,1349039036,
%T A375507 13490390385,134903903876,1349039038789,13490390387923,
%U A375507 134903903879272,1349039038792762,13490390387927663,134903903879276676,1349039038792766810,13490390387927668159
%N A375507 a(1) = 1. For n > 1; a(n) is equal to a(n-1) plus the decimal value of the concatenation of the first n-1 digits of the sequence.
%F A375507 a(n) ~ (c/9)*10^(n-1), where c = Sum_{n>=1} a(n)/10^(n*(n-1)/2) = 1.2141351349... . - _Pontus von Brömssen_, Aug 18 2024
%e A375507 For n = 4 we have that a(n-1) = a(3) = 14 and the decimal value of the concatenation of the first three digits of the sequence is 121, so a(4) = 14 + 121 = 135.
%o A375507 (Python)
%o A375507 from itertools import count
%o A375507 def A375507_list(nmax):
%o A375507     a = [1]
%o A375507     def digits():
%o A375507         for i in count():
%o A375507             for d in str(a[i]):
%o A375507                 yield int(d)
%o A375507     diff = 0
%o A375507     for n,d in enumerate(digits(),1):
%o A375507         if n==nmax: return a
%o A375507         diff = 10*diff+d
%o A375507         a.append(a[-1]+diff) # _Pontus von Brömssen_, Aug 18 2024
%K A375507 nonn,base
%O A375507 1,2
%A A375507 _Rodolfo Kurchan_, Aug 18 2024
%E A375507 a(17)-a(21) from _Pontus von Brömssen_, Aug 18 2024