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A123391
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a(n) = sum of exponents that are primes in the prime factorization of n.
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0
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0, 0, 0, 2, 0, 0, 0, 3, 2, 0, 0, 2, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 3, 2, 0, 3, 2, 0, 0, 0, 5, 0, 0, 0, 4, 0, 0, 0, 3, 0, 0, 0, 2, 2, 0, 0, 0, 2, 2, 0, 2, 0, 3, 0, 3, 0, 0, 0, 2, 0, 0, 2, 0, 0, 0, 0, 2, 0, 0, 0, 5, 0, 0, 2, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 3, 0, 2, 0, 2, 0, 0, 0, 5, 0, 2, 2, 4, 0, 0, 0, 3, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| 36 = 2^2*3^2. Both exponents in this prime factorization are primes. So a(36) = 2+2 = 4.
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MATHEMATICA
| f[n_] := Plus @@ Select[Last /@ FactorInteger[n], PrimeQ]; Table[f[n], {n, 120}] (*Chandler*)
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PROG
| (PARI) {m=105; for(n=1, m, v=factor(n)[, 2]; s=0; for(j=1, #v, if(isprime(v[j]), s=s+v[j])); print1(s, ", "))} - Klaus Brockhaus, Nov 14 2006
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CROSSREFS
| Cf. A101436.
Sequence in context: A113503 A082507 A132349 * A171871 A076260 A135416
Adjacent sequences: A123388 A123389 A123390 * A123392 A123393 A123394
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet, Nov 10 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Nov 11 2006
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