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A056898 a(n) = smallest number m such that m^2+n is prime. 7
1, 0, 0, 1, 0, 1, 0, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 1, 0, 3, 4, 1, 0, 7, 2, 9, 2, 1, 0, 1, 0, 3, 2, 3, 6, 1, 0, 3, 2, 1, 0, 1, 0, 3, 4, 1, 0, 5, 2, 3, 4, 1, 0, 5, 2, 9, 2, 1, 0, 1, 0, 3, 2, 3, 6, 1, 0, 9, 2, 1, 0, 1, 0, 3, 2, 5, 6, 1, 0, 3, 4, 1, 0, 5, 2, 9, 4, 1, 0, 7, 4, 3, 2, 3, 6, 1, 0, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,8

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

a(n) = sqrt(A056896(n)-n) = sqrt(A056897(n)).

For p a prime: a(p) = 0 (and a(p-1) = 1 if p<>3).

EXAMPLE

a(8) = 3 since 3^2+8 = 17 which is prime.

PROG

(PARI) A056898(n) = { my(m=0); while(!isprime((m*m)+n), m++); (m); }; \\ Antti Karttunen, Mar 04 2018

CROSSREFS

Cf. A000040, A002496, A056892, A056893, A056894, A056895, A056896, A056897.

Sequence in context: A242928 A214845 A071960 * A204065 A275281 A204176

Adjacent sequences:  A056895 A056896 A056897 * A056899 A056900 A056901

KEYWORD

nonn

AUTHOR

Henry Bottomley, Jul 05 2000

STATUS

approved

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Last modified August 10 02:28 EDT 2020. Contains 336367 sequences. (Running on oeis4.)