Perimeters of almost-equilateral Heronian triangles.

Terms

a(0) =12a(1) =42a(2) =156a(3) =582a(4) =2172a(5) =8106a(6) =30252a(7) =112902a(8) =421356a(9) =1572522a(10) =5868732a(11) =21902406a(12) =81740892a(13) =305061162a(14) =1138503756a(15) =4248953862a(16) =15857311692a(17) =59180292906a(18) =220863859932a(19) =824275146822