A181963 -id:A181963

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Search: a181963 -id:a181963

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A256302

Least prime p such that p+3*k*(k+1) is prime for all k=0,...,n.

+10
1

2, 5, 5, 5, 11, 11, 11, 11, 11, 11, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23

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

OFFSET

0,1

COMMENTS

Inspired by the so-called prime-generating polynomials.

Since p | 3n(n+1) for n=p-1, one has a(n) > p(n). Otherwise stated, a(p-1) = p (as, e.g., for p=23) is optimal.

LINKS

Table of n, a(n) for n=0..21.

PROG

(PARI) a(n)=forprime(p=1, , for(i=1, n, ispseudoprime(p+3*(i+1)*i)||next(2)); return(p))

CROSSREFS

Cf. A181963, A181969, A181973, A210626, A211773, A212325, ...

Cf. A005846, A056561.

Cf. A256300, A256301.

KEYWORD

nonn,more

AUTHOR

M. F. Hasler, Apr 05 2015

STATUS

approved

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