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A018852
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a(n)^3 is smallest cube beginning with n.
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13
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0, 1, 3, 7, 16, 8, 4, 9, 2, 21, 10, 48, 5, 11, 52, 25, 55, 12, 57, 27, 59, 6, 61, 62, 29, 63, 64, 3, 66, 31, 67, 68, 32, 15, 7, 33, 154, 72, 73, 34, 16, 161, 35, 76, 164, 77, 36, 78, 169, 17, 37, 8, 174, 81, 38, 82, 178, 83, 18, 39, 182, 85, 184, 86, 4, 87, 188, 189, 19, 191, 89, 193, 9
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) >= n^(1/3), for all n > 0, with equality when n is a cube. - Derek Orr, Jul 26 2015
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MAPLE
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f:= proc(n) local d, m;
for d from 0 do
m:= ceil((10^d*n)^(1/3));
if m^3 < 10^d*(n+1) then return m fi
od
end proc:
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PROG
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(Python)
for n in range(1, 10**3):
for k in range(10**3):
if str(k**3).startswith(str(n)):
print(k, end=', ')
break
(PARI) a(n)=k=1; while(k, d=digits(k^3); D=digits(n); if(#D<=#d, c=1; for(i=1, #D, if(D[i]!=d[i], c=0; break)); if(c, return(k))); k++)
vector(100, n, a(n)) \\ Derek Orr, Jul 26 2015
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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