This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A140395 #26 May 29 2019 12:55:32
%S A140395 4,2,2,3,3,4,2,3,3,2,2,5,4,4,4,5,4,4,5,5,3,5,4,4,5,5,5,6,6,5,3,5,5,6,
%T A140395 6,6,5,6,5,7,5,7,6,8,8,8,7,8,7,5,4,6,4,6,4,4,4,6,6,4,3,4,4,5,5,5,6,4,
%U A140395 4,6,4,6,5,6,6,6,6,6,6,5,4,6,5,6,6,5,6
%N A140395 Number of letters in the Hindi word for the number n.
%C A140395 From _Sangeet Paul_, May 29 2019: (Start)
%C A140395 What constitutes a distinct letter is determined by the following rules: all words are in Modern Standard Hindi written in the Devanagari script; a vowel, a vowel diacritic, a consonant, a consonant diacritic, or a nasal diacritic is one letter; a conjunct consonant is as many letters as the consonants conjuncted; a nuqta or a halant is not a letter; and a space between two words is not a letter.
%C A140395 Hindi has a unique word for every number from 0 to 99, and a unique place-value word for 100 and every power of 10 of the form 10^(2k+1) where k is a positive integer. Therefore:
%C A140395 a(n) = a(n mod 100) + (d(100) + a(floor(n/100) mod 10))*[floor(n/100) mod 10 > 0] + Sum_{k=1..oo} (d(10^(2k+1)) + a(floor(n/(10^(2k+1))) mod 100))*[floor(n/(10^(2k+1))) mod 100 > 0] where [] is the Iverson bracket and d() is the number of letters in a place-value word.
%C A140395 d(100) = 2, d(10^3) = 4, d(10^5) = 3, d(10^7) = 4, d(10^9) = 3, d(10^11) = 3, d(10^13) = 3, d(10^15) = 3, d(10^17) = 3.
%C A140395 In another popular convention: a vowel, or a consonant is one letter; a consonant diacritic is half a letter; a conjunct consonant is half a letter plus half as many letters as the consonants conjuncted; and a vowel diacritic, a nasal diacritic, a nuqta, a halant, or a space is not a letter. These rules change the sequence to: 2.5, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 3.5, 3, 3, 3, 3, 3, 3.5, 4, 3.5, 2, ...
%C A140395 (End)
%H A140395 Author?, <a href="http://www.hindidevanagari.com/numbers_saNkhyaaENn.html">Hindi Numbers</a>
%H A140395 Critical Languages Center, Univ. Alabama, <a href="http://bama.ua.edu/~clc/hindi/numbers_hindi.html">Numbers in Hindi</a>
%H A140395 WikiBooks, <a href="http://en.wikibooks.org/wiki/Hindi:Numbers">Hindi Numbers</a>
%H A140395 <a href="/index/Lc#letters">Index entries for sequences related to number of letters in n</a>
%H A140395 <a href="/index/Na">Index entries for sequences related to names of numbers</a>
%Y A140395 Cf. A005589.
%K A140395 nonn,word
%O A140395 0,1
%A A140395 _Vinay Vaishampayan_, Jun 19 2008, Jun 20 2008
%E A140395 Links added by _N. J. A. Sloane_, Jun 20 2008
%E A140395 Offset 0 from _Sangeet Paul_, May 27 2019
%E A140395 a(21)-a(86) from _Sangeet Paul_, May 29 2019