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A063737
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Numbers n such that sum of digits of n is equal to the sum of the prime factors of n, counted with multiplicity.
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9
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2, 3, 4, 5, 7, 27, 378, 576, 588, 648, 729, 2688, 17496, 19683, 49896, 69888, 3796875, 3857868, 4898880, 5878656, 7077888, 8957952, 2499898464, 34998578496, 49997969280, 2928898896840, 7625597484987, 184958866998359685
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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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27=3*3*3, 2+7=9, 3+3+3=9. 49896 = 2*2*2*3*3*3*3*7*11, 4+9+8+9+6 = 36, 2+2+2+3+3+3+3+7+11 = 36.
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MATHEMATICA
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g@n_ := Cases[Union@(Times @@ # & /@Select[Flatten[Table[IntegerPartitions[k, All, Prime@Range@PrimePi@(9*n)], {k, 1, 9*n}], 1], Plus@@#==DigitSum@(Times @@ #) &]),
_?(#<10^n&)];
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PROG
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(ARIBAS): var stk: stack; end; for n := 1 to 2000000 do s := itoa(n); for j := 0 to length(s) - 1 do stack_push(stk, atoi(s[j..j])); end; if sum(stack2array(stk)) = sum(factorlist(n)) then write(n, " "); end; end; .
(PARI) isok(m) = my(f=factor(m)); sumdigits(m) == f[, 1]~*f[, 2]; \\ Michel Marcus, Dec 18 2020
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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