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 A219653 #8 Nov 25 2012 23:56:05 %S A219653 0,1,2,4,6,8,12,16,20,24,26,30,34,38,42,48,52,56,60,66,72,78,84,90,96, %T A219653 102,108,116,120,122,126,130,134,138,144,148,152,156,162,168,174,180, %U A219653 186,192,198,204,212,218,226,234,240,244,248,252,258,264,270,276 %N A219653 Least inverse of A219652; a(n) = minimal i such that A219652(i) = n. %H A219653 A. Karttunen, <a href="/A219653/b219653.txt">Table of n, a(n) for n = 0..10080</a> %o A219653 (Scheme with _Antti Karttunen_'s Intseq-library, three different variants): %o A219653 (define A219653 (MATCHING-POS 0 0 (lambda (i) (or (< i 1) (not (= (A219652 (- i 1)) (A219652 i))))))) %o A219653 (define A219653v2 (LEAST-I-WITH-FUN-I-EQ-N 0 0 A219652)) ;; Slow! %o A219653 (define A219653v3 (RECORD-POS 0 0 A219652)) %Y A219653 Cf. A219655 for the greatest inverse. A219654 gives the first differences. %Y A219653 This sequence is based on Factorial number system: A007623. Analogous sequence for binary system: A213708 and for Zeckendorf expansion: A219643. Cf. A219652, A219659, A219666. %K A219653 nonn %O A219653 0,3 %A A219653 _Antti Karttunen_, Nov 25 2012