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A052021
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Sum of digits of n is the largest prime factor of n.
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7
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2, 3, 5, 7, 12, 50, 70, 308, 320, 364, 476, 500, 605, 700, 704, 715, 832, 935, 1088, 1183, 1547, 1729, 2401, 2584, 2618, 2704, 2926, 3080, 3200, 3536, 3640, 3952, 4225, 4760, 4784, 4913, 5000, 5491, 5525, 5819, 5831, 6050, 6175, 6517, 6647, 7000, 7040, 7150
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
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FORMULA
| {n: A007953(n) = A006530(n)}. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 30 2010]
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EXAMPLE
| E.g. 13685 has sum of digits '23' and 13685 = 5.7.17.'23'.
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MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 30 2010: (Start)
A007953 := proc(n) add(d, d=convert(n, base, 10)) ; end proc:
A006530 := proc(n) numtheory[factorset](n) ; max(op(%)) ; end proc:
for n from 1 to 8000 do if A007953(n) = A006530(n) then printf("%d, ", n) ; end if; end do: (End)
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PROG
| (Haskell)
a052021 n = a052021_list !! (n-1)
a052021_list = tail $ filter (\x -> a007953 x == a006530 x) [1..]
-- Reinhard Zumkeller, Nov 06 2011
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CROSSREFS
| Cf. A052018, A052019, A052020, A052022, A007953, A005349, A028834.
Sequence in context: A024784 A060528 A117593 * A126057 A126056 A126055
Adjacent sequences: A052018 A052019 A052020 * A052022 A052023 A052024
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KEYWORD
| nonn,base,nice
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AUTHOR
| Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 15 1999.
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EXTENSIONS
| Single-digit primes added by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 30 2010
Offset corrected by Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 05 2011
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