A028505 -id:A028505 - cp's OEIS frontend

A080122 Number of primes less than n*10^13.

346065536839, 675895909271, 1000121668853, 1320811971702, 1638923764567, 1955010428258, 2269432871304, 2582444113487, 2894232250783, 3204941750802, 3514687156436, 3823561506566, 4131641836725, 4438993433550, 4745670621117

Offset: 1

Robert G. Wilson v and Jeff Burch, Jan 29 2003

nonn

Robert G. Wilson v, Table of n, a(n) for n = 1..10000
Thomas R. Nicely, Some Results of Computational Research in Prime Numbers [See local copy in A007053]
Tomás Oliveira e Silva, Tables of values of pi(x) and of pi2(x)
Andrew R. Booker, The Nth Prime Page

Cf. A038801, A028505, A038812, A038813, A038814, A038815, A038816, A038817, A038818, A038819, A038820, A038821, A080123, A080124, A080125, A080126, A080127, A080128, A080129.

Mathematica
```
Table[ PrimePi[ n*10^13 ], {n, 1, 9}]
```

a(n)=primepi(10^13*n) \\ Charles R Greathouse IV, Apr 29 2015

A116356 Number of primes less than n*10^21.

Original entry on oeis.org

21127269486018731928, 41644391885053857293, 61943374158983520871, 82103246362658124007, 102160925813497229402, 122137912741771709423, 142048291427909819758, 161902001837504830333, 181706431926947074426, 201467286689315906290

Offset: 1

Robert G. Wilson v, Feb 04 2006

nonn

Chai Wah Wu, Table of n, a(n) for n = 1..53
Thomas R. Nicely, Some Results of Computational Research in Prime Numbers [See local copy in A007053]

Cf. A000720, A038801, A028505, A038812, A038813, A038814, A038815, A038816, A038817, A038818, A038819.

Cf. A038820, A038821, A038822, A080123, A080124, A080125, A080126, A080127, A080128, A080129.

A381020 a(n) = A381018(100*n).

Original entry on oeis.org

30, 45, 60, 75, 92, 106, 119, 133, 141, 157, 170, 177, 185, 204, 224, 236, 245, 260, 275, 292, 305, 318, 330, 342, 359, 371, 382, 390, 405, 419, 430, 444, 457, 472, 490, 507, 524, 535, 550, 561, 570, 583, 593, 604, 611, 621, 627, 638, 647, 659, 670, 679, 683, 697

Offset: 1

Michel Marcus, Feb 12 2025

nonn

Thomas Ehrenborg, Gauss Circle Primes, arXiv:2502.06804 [math.GM], 2025. See Table 2 p. 4.

Cf. A028505, A381018.

from math import isqrt
from sympy import isprime
def A381020(n): return sum(1 for m in range(1,100*n+1) if isprime(1+(sum(isqrt(k*((m<<1)-k)) for k in range(1,m+1))<<2))) # Chai Wah Wu, Feb 13 2025

More terms from Jinyuan Wang, Feb 13 2025

A182564 Number of primes < Fibonacci(n).

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 4, 5, 8, 11, 16, 23, 34, 50, 74, 111, 166, 250, 376, 574, 871, 1329, 2033, 3120, 4794, 7396, 11425, 17688, 27426, 42612, 66317, 103298, 161207, 251757, 393790, 616645, 966507, 1516410, 2381429, 3743010, 5888201, 9269519, 14604028, 23023555, 36322186, 57337078, 90565070, 143130478

Offset: 0

Alex Ratushnyak, May 05 2012

nonn

			Fibonacci(7)=13, there are 5 primes less than 13, so a(7)=5.

Cf. A000040, A000045, A006880, A007053, A028505, A038107, A040014.

Table[If[PrimeQ[Fibonacci[n]],PrimePi[Fibonacci[n]-1],PrimePi[ Fibonacci[ n]]],{n,0,50}] (* Harvey P. Dale, Feb 12 2022 *)

a(n) = primepi(fibonacci(n)-1) \\ Michel Marcus, May 13 2013

cp's OEIS Frontend

A080122 Number of primes less than n*10^13.

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A116356 Number of primes less than n*10^21.

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A381020 a(n) = A381018(100*n).

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A182564 Number of primes < Fibonacci(n).

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