1,2,3,4,5,6,7,8,9,110,121,132,143,154,165,176,187,198,109,220,231,242,253,264,275,286,297,208,219,330,341,352,363,374,385,396,307,318,329,440,451,462,473,484,495,406,417,428,439,550,561,572,583,594

def a(n):
    s = str(n)
    if len(s) < 2: return n
    res = []
    for i in range(len(s) - 1):
        d1, d2 = int(s[i]), int(s[i+1])
        res.append(s[i])
        res.append(str((d1 + d2) % 10))
    res.append(s[-1])
    return int("".join(res))
print([a(n) for n in range(1, 55)])

a[n_]:=Module[{d=IntegerDigits[n]},l=Length[d];If[l==1,n,Do[j=2i;d=Insert[d,Mod[d[[j-1]]+d[[j]],10],j],{i,l-1}];FromDigits[d]]];Array[a,54] (* _James C. McMahon_, Apr 25 2026 *)