/^>/{val=$0;next} length($0)>=15{print val ORS $0;val=""}
L14+L3t2YWw9JDA7bmV4dH0gbGVuZ3RoKCQwKT49MTV7cHJpbnQgdmFsIE9SUyAkMDt2YWw9IiJ9
Jmd0O05CNTAxMzY1OjUwODpISkYySEJHWEY6MToxMjEwMjoxNDQwMToxNDk1NyAxOk46MDpDVFRHVEEKR0FBVENUVENBVEdUR0FHR0FBQ0FHQUFUVENBR0MKJmd0O05CNTAxMzY1OjUwODpISkYySEJHWEY6MToxMjEwMjoxNzY3MToxNDk1NyAxOk46MDpDVFRHVEEKQVRDR1RHCiZndDtOQjUwMTM2NTo1MDg6SEpGMkhCR1hGOjE6MTIxMDI6MTQ0MDE6MTQ5NTcgMTpOOjA6Q1RUR1RBCkNDQ0NDQ0NDQ0dHR0dDVENHR0dHR0dHQ1RHRw==
>NB501365:508:HJF2HBGXF:1:12102:14401:14957 1:N:0:CTTGTA
GAATCTTCATGTGAGGAACAGAATTCAGC
>NB501365:508:HJF2HBGXF:1:12102:17671:14957 1:N:0:CTTGTA
ATCGTG
>NB501365:508:HJF2HBGXF:1:12102:14401:14957 1:N:0:CTTGTA
CCCCCCCCCGGGGCTCGGGGGGGCTGG