Revision as of 19:38, 17 March 2021 (view source) rosettacode>Lambertdw (→‎{{header\|J}}) ← Older edit		Revision as of 21:25, 17 March 2021 (view source) rosettacode>Lambertdw (→‎{{header\|J}}) Newer edit →
Line 377: spds=:([:sum_of_proper_divisors"0(#\@i.-.i.&.:(p:inv))@*:)f. NB. remove primes which contribute 1 </lang> We may revisit to correct the larger untouchable tallies. JThe ~~is an algorithm description language. The~~straightforward algorithm presented is ~~straightforward and~~ a little bit efficient, and, I claim, the verb <tt>(candidates-.spds)</tt> produces the full list of untouchable numbers up to its argument. It considers the sum of proper divisors through the argument squared, less primes. Since J is an algorithm description language, it may be "fairer" to state in J that "more resources required" than in some other language. [https://www.eecg.utoronto.ca/~jzhu/csc326/readings/iverson.pdf] Time (seconds) and space (bytes) on a high end six year old (new in 2015) laptop computer. <pre> timespacex'(-.candidates@#)/:~~.spds 10000' 600.285 4.29497e9 </pre> <pre> UNTOUCHABLES=:(candidates-.spds) 2000 NB. compute untouchable numbers Line 400 ⟶ 406: 1884 1888 1894 1896 1920 1922 1944 1956 1958 1960 1962 1972 1986 1992 SBD=:spds 10000 NB. sums of proper divisors of many integers T=:/:~~.SBD NB. sort the nub #T NB. leaving this many touchable numbers, which are dense through at least 10000 47269787 U=:(-.~candidates@#)T NB. possible untouchable numbers head=: ~~(<;._1~~~ 'n';'~~&=)';n;~~tally of possible untouchable numbers to n' head,:,.L:0;/\|:(,.U&I.)10^#\i.5 NB. testing to ten thousand squared ┌──────┬──────────────────────────────────────────┐

Untouchable numbers: Difference between revisions

Untouchable numbers (view source)

Revision as of 21:25, 17 March 2021