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 A257803 #10 May 13 2015 15:43:38 %S A257803 1,4,7,9,12,17,18,21,23,24,25,27,30,34,35,38,41,42,49,52,53,54,55,57, %T A257803 60,64,65,68,70,73,74,75,76,77,81,82,83,90,93,95,96,103,106,107,108, %U A257803 109,111,114,118,119,122,127,128,131,132,134,136,137,138,139,140,145,147,148,149,150,151,155,156,157,164,167,168,171 %N A257803 Positions of odd numbers in A233271, the infinite trunk of inverted binary beanstalk. %H A257803 Antti Karttunen, <a href="/A257803/b257803.txt">Table of n, a(n) for n = 1..7973</a> %F A257803 Other identities: %F A257803 For all n >= 1, A257807(a(n)) = n. [A257807 works as a left inverse for this injective function.] %o A257803 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A257803 (define A257803 (MATCHING-POS 1 1 (lambda (n) (odd? (A233271 n))))) %o A257803 (define A257803 (MATCHING-POS 1 1 (lambda (n) (odd? (A257800 n))))) %Y A257803 Complement: A257804. %Y A257803 Cf. A233271, A257800, A257806, A257807. %K A257803 nonn %O A257803 1,2 %A A257803 _Antti Karttunen_, May 12 2015