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 A172007 #3 Jul 22 2025 07:32:21 %S A172007 25,32,40,49,50,51,52,54,62,64,67,72,79,81,82,85,92,96,100,102,122, %T A172007 127,128,129 %N A172007 Numbers which require a - in their minimal SNUSP representation. %C A172007 SNUSP is a programming language where each command is an individual letter. The four of concern here are +, -, @ and #. + increments the current data value, - decrements it, @ is a "subroutine call" and # is a "return". When an @ is encountered, a record of the location is put on a stack and execution continues. When a # is encountered, if there is a return point on the stack, the execution continues at that a single character beyond that return point. If there is no return point on the stack, execution terminates. %C A172007 Thus "@@++#" would put the first two "@" return points on the stack, increment data twice, return from the second "@" to the last "+", increment the data once more, return from the first "@" to the first "+", increment the data two more times and finally terminate when it hits the "#" with no return points on the stack. The data is always initialized to zero so this effectively puts 5 into the data. In order to place a particular value into the data, there is a minimal string of these characters. In some cases, allowing the '-' command can shorten this minimal string. This sequence is a list of numbers which require a - in their minimal sequence. All the numbers represented in the above sequence save at most 2 characters by allowing the -. Whether this is a maximum savings and whether the savings can be arbitrarily large is not known (at least not to me). %H A172007 <a href="http://www.esolangs.org/wiki/SNUSP">SNUSP - Esolang</a> %H A172007 <a href="http://c2.com/cgi/wiki?SnuspLanguage">SNUSP Language</a> %e A172007 Using both + and -, 25 can be represented as @-@@@+++# but if we only allow +, the minimal program is @++@@++++# so we only need 8 characters if we allow both + and - but 9 if we allow only + so that 25 requires a - in its minimal representation. It is the first value with this property and so is the first value in our sequence. %p A172007 See A172005. %Y A172007 A172005, A172006 %K A172007 nonn %O A172007 1,1 %A A172007 Darrell Plank (jar_czar(AT)msn.com), Jan 22 2010