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A089761 Smallest k such that k*i^2 + 1 is prime for i = 1 to n. 0
1, 1, 4, 22, 58, 58, 58, 54972, 68112, 4748632, 861066640, 861066640, 861066640, 861066640, 861066640 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(16) > 1.4*10^13. [Max Alekseyev]

LINKS

Table of n, a(n) for n=1..15.

MAPLE

for n from 1 to 10 do for k from 1 do f:=0: for i from 1 to n do if not isprime(k*i^2+1) then f:=1: break fi od: if f=0 then printf("%d, ", k): break fi od od: # C. Ronaldo

CROSSREFS

Cf. A124417.

Sequence in context: A050773 A122241 A076525 * A098837 A104171 A036924

Adjacent sequences:  A089758 A089759 A089760 * A089762 A089763 A089764

KEYWORD

hard,more,nonn

AUTHOR

Amarnath Murthy, Nov 22 2003

EXTENSIONS

Corrected and extended by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 26 2004

a(11)-a(15) from Donovan Johnson, Sep 27 2008

STATUS

approved

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Last modified October 14 02:19 EDT 2019. Contains 327994 sequences. (Running on oeis4.)