#Mathematica, 71 bytes
Mathematica, 71 bytes
""<>s[[i]]~t~If[i~Mod~#2==1,#2,1]~(t=Table)~{i,Tr[1^(s=Characters@#)]}&
saved -2 bytes by listening to user202729
#Mathematica, 71 bytes
""<>s[[i]]~t~If[i~Mod~#2==1,#2,1]~(t=Table)~{i,Tr[1^(s=Characters@#)]}&
saved -2 bytes by listening to user202729
Mathematica, 71 bytes
""<>s[[i]]~t~If[i~Mod~#2==1,#2,1]~(t=Table)~{i,Tr[1^(s=Characters@#)]}&
saved -2 bytes by listening to user202729
#Mathematica, 7271 bytes
""<>(t=Table)[s[[i]]~t~If[i~Mod~#2==1""<>s[[i]]~t~If[i~Mod~#2==1,#2,1],1]~(t=Table)~{i,Length[s=Characters@#]Tr[1^(s=Characters@#)]}]&&
saved -2 bytes by listening to user202729
#Mathematica, 72 bytes
""<>(t=Table)[s[[i]]~t~If[i~Mod~#2==1,#2,1],{i,Length[s=Characters@#]}]&
saved -2 bytes by listening to user202729
#Mathematica, 71 bytes
""<>s[[i]]~t~If[i~Mod~#2==1,#2,1]~(t=Table)~{i,Tr[1^(s=Characters@#)]}&
saved -2 bytes by listening to user202729
#Mathematica, 7472 bytes
""<>(t=Table)[#~StringTake~{i}~t~If[i~Mod~#2==1[s[[i]]~t~If[i~Mod~#2==1,#2,1],{i,StringLength@#Length[s=Characters@#]}]&
saved -2 bytes by listening to user202729
#Mathematica, 74 bytes
""<>(t=Table)[#~StringTake~{i}~t~If[i~Mod~#2==1,#2,1],{i,StringLength@#}]&
#Mathematica, 72 bytes
""<>(t=Table)[s[[i]]~t~If[i~Mod~#2==1,#2,1],{i,Length[s=Characters@#]}]&
saved -2 bytes by listening to user202729