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 A172008 Count of minimal SNUSP programs using +, @ and # to yield N 1
 1, 1, 2, 2, 2, 2, 2, 2, 4, 4, 4, 4, 2, 4, 2, 2, 4, 2, 6, 2, 2, 2, 8, 8, 4, 2, 2, 2, 2, 2, 2, 6, 2, 2, 10, 10, 4, 2, 8, 8, 2, 2, 4, 8, 2, 2, 2, 6, 14, 2, 4, 4, 8, 8, 2, 4, 2, 4, 2, 2, 2, 4, 6, 6, 2, 2, 2, 2, 4, 4, 18, 18, 2, 2, 4, 2, 8, 2, 10, 2, 2, 2, 4, 4, 6, 4, 4, 4, 2, 2, 2, 4, 6, 6, 2, 2, 2, 8, 2, 2, 6, 6, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Shortest SNUSP representation of a number using only + and @ is in A172005. SNUSP is a programming language where each command is an individual letter. The three of concern here are + and @ and #. + increments the current data value, @ 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. 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 one or more minimal strings of these characters. The i'th element of the sequence gives the number of minimal SNUSP programs using only these characters. After 2, all sequences end in either +++ or @++ both of which are equivalent so that all values above a(2) are even. LINKS EXAMPLE 19 can be represented minimally in 6 ways using @, + and #: @+@+++++# +@@@++++# @++@@+++# @+@++@++# +@@@+@++# @++@@@++# Thus a(19) = 6. MAPLE See A172005 CROSSREFS Sequence in context: A268045 A118177 A105069 * A100825 A216452 A307616 Adjacent sequences:  A172005 A172006 A172007 * A172009 A172010 A172011 KEYWORD nonn AUTHOR Darrell Plank (jar_czar(AT)msn.com), Jan 22 2010 STATUS approved

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Last modified August 10 02:26 EDT 2020. Contains 336366 sequences. (Running on oeis4.)