

A319228


Number of primes of the form b^2 + b + 1 for b <= 10^n.


1



6, 32, 189, 1410, 10751, 88118, 745582, 6456835, 56988601, 510007598, 4615215645
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..11.


EXAMPLE

a(1) = 6 because there are 6 primes of the form b^2 + b + 1 for b <= 10: 3, 7, 13, 31, 43 and 73.


PROG

(PARI) {a(n) = sum(k=0, 10^n, isprime(k^2+k+1))}
(Python)
from sympy import isprime
def A319228(n):
c, b, b2, n10 = 0, 1, 3, 10**n
while b <= n10:
if isprime(b2):
c += 1
b += 1
b2 += 2*b
return c # Chai Wah Wu, Sep 17 2018


CROSSREFS

Cf. A002383, A002384, A206709.
Sequence in context: A238115 A228959 A302734 * A216441 A108188 A020058
Adjacent sequences: A319225 A319226 A319227 * A319229 A319230 A319231


KEYWORD

nonn,more


AUTHOR

Seiichi Manyama, Sep 14 2018


EXTENSIONS

a(10) from Chai Wah Wu, Sep 17 2018
a(11) from Chai Wah Wu, Sep 18 2018


STATUS

approved



