Number of 5-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero.

Terms

a(0) =7a(1) =45a(2) =155a(3) =415a(4) =905a(5) =1755a(6) =3085a(7) =5077a(8) =7891a(9) =11761a(10) =16887a(11) =23555a(12) =32005a(13) =42575a(14) =55545a(15) =71305a(16) =90175a(17) =112597a(18) =138931a(19) =169671a(20) =205217a(21) =246115a(22) =292805a(23) =345885a(24) =405835a(25) =473305a(26) =548815a(27) =633067a(28) =726621a(29) =830231