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J, 50 bytes {{({~[:y&(i.&1@:=)[:>+/&.>),{@(,&<)~p:i.p:^:_1 y}} Try it online! A nasty DD solution. {{({~[:y&(i.&1@:=)[:>+/&.>),{@(,&<)~p:i.p:...
Answer
#1: Initial revision
by
south
·
2022-03-03T19:50:01Z (over 2 years ago)
# [J](https://jsoftware.com/#/), 50 bytes
```J
{{({~[:y&(i.&1@:=)[:>+/&.>),{@(,&<)~p:i.p:^:_1 y}}
```
[Try it online!](https://tio.run/##y/r/P83WyljBSkFdo7ou2qpSTSNTT83QwcpWM9rKTltfTc9OU6faQUNHzUazrsAqU6/AKs4q3lChUh2oUSE1MTlDwUTBTMHIRMHQyEDB0MDAAAA)
A nasty DD solution.
```
{{({~[:y&(i.&1@:=)[:>+/&.>),{@(,&<)~p:i.p:^:_1 y}}
p:i.p:^:_1 NB. primes less than y
{@(,&<) NB. cartesian product, 2d array of boxed pairs
, NB. flatten boxes
({~[:y&(i.&1@:=)[:>+/&.>) NB. monadic hook
[:>+/&.> NB. sum each pair and unbox
[:y&(i.&1@:=) NB. first occurrence of y in list of sums
{~ NB. flip arguments to index boxed pairs
```