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A217390
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Numbers n such that sum of squares of digits of n equals the sum of prime divisors of n.
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3
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12, 581, 1014, 1036, 1180, 1272, 1746, 2553, 3420, 3741, 4140, 4544, 5104, 5238, 5313, 5966, 7134, 7272, 8174, 8346, 8549, 9153, 9525, 9536, 10476, 11070, 11800, 12350, 12882, 13481, 13702, 14045, 15341, 15974, 16415, 16999, 17051, 17220, 17444, 18361, 18798
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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581 = 7*83 is in the sequence because 5^2 + 8^2 + 1^2 = 7 + 83 = 90.
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MAPLE
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with(numtheory):A:= proc(n) add(u^2, u=convert(n, base, 10)) ; end proc: for i from 2 to 20000 do:x:=factorset(i):n1:=nops(x): s:=sum('x[i] ', 'i'=1..n1):if s=A(i) then printf(`%d, `, i):else fi:od:
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MATHEMATICA
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Rest[Select[Range[20000], Total[Transpose[FactorInteger[#]][[1]]]==Total[IntegerDigits[#]^2]&]]
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PROG
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(PARI) ok(n)={vecsum(factor(n)[, 1]) == vecsum(apply(d->d^2, digits(n)))} \\ Andrew Howroyd, Feb 25 2018
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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