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A276476 a(n) is the number of distinct integers of the form x^2-x-prime(n) for 0<=x<=prime(n)+1 whose absolute value is prime. 0
1, 2, 3, 5, 6, 9, 9, 13, 11, 17, 20, 17, 10, 32, 16, 23, 26, 30, 25, 21, 55, 38, 30, 27, 25, 34, 57, 19, 83, 49, 44, 40, 39, 60, 37, 77, 54, 57, 27, 43, 79, 67, 45, 110, 42, 93, 79, 79, 43, 85, 46, 90, 96, 41, 54, 96, 127, 107, 63, 78, 181, 67, 78, 72, 189, 51, 77, 103 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..68.

EXAMPLE

a(2)=2 because prime(2)=3 and x^2 - x - 3 generates {-3, -3, -1, 3, 9}. This contains two integers, -3 and 3, whose absolute value is prime.

a(14)=32 because prime(14)=43 and x^2 - x - 43 generates 32 prime numbers for x = 0..44.

PROG

(PARI) isaprime(x) = isprime(x) || isprime(-x);

nbp(n) = {v = vector(prime(n)+2, x, x--; x^2-x-prime(n)); vp = select(x->isaprime(x), v); vp = Set(vp); #vp; } \\ Michel Marcus, Sep 13 2016

CROSSREFS

Cf. A014556, A253827.

Sequence in context: A053784 A036697 A131292 * A069880 A230044 A069861

Adjacent sequences:  A276473 A276474 A276475 * A276477 A276478 A276479

KEYWORD

nonn

AUTHOR

Charles Kusniec, Sep 12 2016

EXTENSIONS

More terms from Michel Marcus, Sep 13 2016

STATUS

approved

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Last modified November 12 05:52 EST 2019. Contains 329051 sequences. (Running on oeis4.)