A353134 a(n) = PrimePi(n*SumOfDigits(n)).

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

Offset

1,2

Links

Table of n, a(n) for n=1..63.

Formula

a(n) = A000720(A057147(n)).

Example

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.

Mathematica

Table[PrimePi[n Total[IntegerDigits[n]]], {n, 100}]

Prog

(Python)
from sympy import primepi
def a(n): return primepi(n*sum(map(int, str(n))))
print([a(n) for n in range(1, 65)]) # Michael S. Branicky, Apr 25 2022
(PARI) a(n) = primepi(n*sumdigits(n)); \\ Michel Marcus, Apr 25 2022

Crossrefs

Cf. A000720, A007953, A057147, A353126.

Sequence in context: A054519 A168434 A300416 * A377283 A038107 A377057

Adjacent sequences: A353131 A353132 A353133 * A353135 A353136 A353137

Keyword

nonn,base

Author

Tanya Khovanova, Apr 25 2022

Status

approved