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A176707
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Sum of digits of all distinct prime factors of n-th semiprime.
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2
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2, 5, 3, 7, 9, 8, 10, 4, 5, 6, 5, 10, 12, 12, 7, 7, 7, 11, 7, 13, 13, 6, 9, 8, 12, 9, 7, 13, 9, 14, 11, 7, 13, 15, 10, 13, 10, 16, 15, 2, 9, 8, 10, 17, 15, 14, 10, 6, 16, 12, 9, 18, 11, 12, 13, 4, 17, 19, 10, 15, 10, 18, 16, 4, 18, 10, 6, 12, 11, 10, 12, 11, 12, 13, 12, 7, 16, 19, 14, 14, 7
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(1)=2 because 1st semiprime=2*2 and 2=2; a(2)=5 because 2nd semiprime=2*3 and 2<3.
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MAPLE
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A007953 := proc(n) add(d, d=convert(n, base, 10)) ; end proc:
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PROG
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(Python)
from sympy import factorint
def aupton(terms):
alst, m = [], 4
while len(alst) < terms:
f = factorint(m)
if sum(f.values()) == 2: # semiprime
alst.append(sum(sum(map(int, str(p))) for p in f.keys()))
m += 1
return alst
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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