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A353134
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a(n) = PrimePi(n*SumOfDigits(n)).
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1
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0, 2, 4, 6, 9, 11, 15, 18, 22, 4, 8, 11, 15, 19, 24, 29, 32, 37, 42, 12, 18, 23, 30, 34, 40, 46, 53, 59, 66, 24, 30, 37, 45, 51, 59, 66, 73, 80, 91, 37, 46, 54, 62, 70, 79, 88, 97, 105, 115, 53, 62, 72, 82, 92, 101, 112, 124, 133, 143, 72, 82, 94, 103
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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Consider number 2: The sum of digits of 2 equals 2; 2*2 = 4; The number of primes not exceeding 4 is 2. Thus a(2) = 2.
Consider number 11: 11*SOD(11) = 22; PrimePi(22) = 8. Thus, a(11) = 8.
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MATHEMATICA
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Table[PrimePi[n Total[IntegerDigits[n]]], {n, 100}]
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PROG
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(Python)
from sympy import primepi
def a(n): return primepi(n*sum(map(int, str(n))))
(PARI) a(n) = primepi(n*sumdigits(n)); \\ Michel Marcus, Apr 25 2022
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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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STATUS
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approved
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