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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 2 16:02 EDT 2020. Contains 335404 sequences. (Running on oeis4.)