A065774 Numbers k such that the product of the digits of k is equal to the sum of the prime factors of k, counted with multiplicity.
2, 3, 4, 5, 7, 18, 25, 154, 329, 418, 442, 532, 1519, 1826, 2354, 2472, 2781, 3383, 4343, 4712, 5282, 5561, 6171, 6623, 7922, 9331, 9911, 11248, 12328, 12773, 13125, 14193, 15194, 16512, 17267, 19852, 21479, 24516, 26522, 31816, 32661, 36512
Offset: 1
Links
- Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 400 terms from Harry J. Smith)
Programs
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Mathematica
Select[Range[2, 10^5], Times @@ IntegerDigits @ # == Plus @@ Times @@@ FactorInteger @ # &] (* Giovanni Resta, Apr 23 2017 *)
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PARI
ProdD(x)= { local(p=1); while (x>9 && p>0, p*=(x-10*(x\10)); x\=10); return(p*x) } sopfr(n)= { local(f,s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]*f[i, 2]); return(s) } { n=0; for (m=1, 10^9, if (ProdD(m) == sopfr(m), write("b065774.txt", n++, " ", m); if (n==400, return)) ) } \\ Harry J. Smith, Oct 30 2009
Extensions
Offset changed from 0 to 1 by Harry J. Smith, Oct 30 2009
Comments