A014569 Super-3 Numbers (3n^3 contains substring '333' in its decimal expansion).
261, 462, 471, 481, 558, 753, 1036, 1046, 1471, 1645, 1752, 1848, 1923, 1926, 1968, 2031, 2231, 2232, 2363, 2395, 2471, 2591, 2610, 3058, 3087, 3148, 3163, 3172, 3181, 3471, 3494, 3542, 3851, 3884, 4143, 4269, 4314, 4471, 4527, 4554, 4620, 4710, 4732
Offset: 1
Examples
1752 is in the sequence since 3 * 1752^3 = 161'333'13024.
References
- C. A. Pickover, Keys to Infinity. New York: Wiley, p. 7, 1995.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
- Giovanni Resta, super-d numbers, personal web site "Numbers Aplenty", 2013.
- Eric Weisstein's World of Mathematics, Super-d Number.
Programs
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Mathematica
Select[Range[5000],MemberQ[Partition[IntegerDigits[3#^3],3,1],{3,3,3}]&] (* Harvey P. Dale, Feb 01 2013 *)
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PARI
select( {is_A014569(n, d=3, m=10^d, r=m\9*d)=n=d*n^d; until(r>n\=10, n%m==r && return(1))}, [0..4999]) \\ Using the (optional) 2nd arg d=2..9 allows to compute the sequences A032743-A032749. - M. F. Hasler, Jul 16 2024
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Python
is_A014569=lambda n, d=3: str(d)*d in str(d*n**d) # M. F. Hasler, Jul 16 2024
Formula
n < a(n) < 200n for n > 2. - Charles R Greathouse IV, Dec 04 2024
Extensions
Corrected and extended by Patrick De Geest, May 15 1998
Offset changed to 1 by M. F. Hasler, Jul 16 2024
Comments