This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
a(4) = 1012 hence a(5)=10120 and a(6) = 101202.
a(8) = 6 because 8*6 = 48 and 6 is the minimum number that multiplied by 8 gives a number ending in 8. a(12) = 26 because 12*26 = 312 and 26 is the minimum number that multiplied by 12 gives a number ending in 12.
P:=proc(n) local a,b,i,j; print(11); for i from 2 by 1 to n do b:=trunc(evalf(log10(i)))+1; for j from 2 by 1 to n do a:=i*j; if i=a-trunc(a/10^b)*10^b then print(j); break; fi; od; od; end: P(101); # Paolo P. Lava, Apr 11 2008
snrd[n_]:=Module[{k=2},While[Mod[k*n,10^IntegerLength[n]]!=n,k++];k]; Array[ snrd,70] (* Harvey P. Dale, Apr 08 2019 *)
def a(n):
kn, s = 2*n, str(n)
while not str(kn).endswith(s): kn += n
return kn//n
print([a(n) for n in range(1, 66)]) # Michael S. Branicky, Nov 06 2021
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