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Explore Stack Internal #J, 19 15 bytes
>.@(%&3)*1-3|<: Probably need to golf this further...
1-indexed.
###Ungolfed:
>> choose_sign =: 1-3|<: NB. 1-((n-1)%3) >> choose_magnitude =: >.@(%&3) NB. ceil(n/3) >> f =: choose_sign * choose_magnitude >> f 1 12 77 << 1 _4 0 Where >> means input (STDIN) and << means output (STDOUT).
#J, 19 15 bytes
>.@(%&3)*1-3|<: Probably need to golf this further...
1-indexed.
###Ungolfed:
>> choose_sign =: 1-3|<: NB. 1-((n-1)%3) >> choose_magnitude =: >.@(%&3) NB. ceil(n/3) >> f =: choose_sign * choose_magnitude >> f 1 12 77 << 1 _4 0 Where >> means input (STDIN) and << means output (STDOUT).
>.@(%&3)*1-3|<: Probably need to golf this further...
1-indexed.
>> choose_sign =: 1-3|<: NB. 1-((n-1)%3) >> choose_magnitude =: >.@(%&3) NB. ceil(n/3) >> f =: choose_sign * choose_magnitude >> f 1 12 77 << 1 _4 0 Where >> means input (STDIN) and << means output (STDOUT).
#J, 19 15 bytes
>.@(%&3)*1-3|<: Probably need to golf this further...
1-indexed.
###Ungolfed:
>> choose_sign =: 1-3|<: NB. 1-((n-1)%3) >> choose_magnitude =: >.@(%&3) NB. ceil(n/3) >> f =: choose_sign * choose_magnitude >> f 1 12 77 << 1 _4 0 Where >> means input (STDIN) and << means output (STDOUT).