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A156622
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Values of register a when register b becomes 0 for the two register machine {i[1], i[1], i[1], d[2,1], d[1,6], i[2], d[1,5], d[2,3]}
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0
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1, 4, 7, 13, 22, 34, 52, 79, 121, 184, 277, 418, 628, 943, 1417, 2128, 3193, 4792, 7189, 10786, 16180, 24271, 36409, 54616, 81925, 122890, 184336
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The instructions of this two register counting machine are to be interpreted as follows: Two registers are initialized to zero, and the instruction pointer starts on the first instruction. i[k] means increment the k-th register. The instruction pointer then moves to the next instruction. d[k,l] means decrement the k-th register if it is nonzero, and then change the instruction pointer to l. Otherwise move the instruction pointer to the next instruction. The following set of 8 instructions is given in the book 'A New Kind of Science' by Stephen Wolfram as one of the simplest register machines which has complex behaviour. {i[1], i[1], i[1], d[2,1], d[1,6], i[2], d[1,5], d[2,3]} This sequence distils information about the states of the register machine by including only the values of the first register, at those times when the 2nd register has just been decremented to zero.
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REFERENCES
| Wolfram, S., A New Kind of Science. Champaign, IL: Wolfram Media, pp. 97-102, 2002.
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CROSSREFS
| Sequence in context: A190845 A190805 A008471 * A111314 A139217 A038391
Adjacent sequences: A156619 A156620 A156621 * A156623 A156624 A156625
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KEYWORD
| nonn
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AUTHOR
| Jack Grahl (jgrahl(AT)math.ucl.ac.uk), Feb 11 2009
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