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A119752 a(1)=2; a(n)=first even number greater than a(n-1) such that a(i)+a(n)+1 is prime for all i=1,2,...,n. 9
2, 8, 14, 44, 224, 638, 1274, 4004, 675404, 2203958, 3075158, 6195234164, 77989711184, 4566262987328 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MAPLE
R:= [2]: count:= 1:
for k from 4 by 2 while count < 11 do
if isprime(2*k+1) and andmap(isprime, [seq(R[i]+k+1, i=1..count)]) then
R:= [op(R), k]; count:= count+1
fi
od:
R; # Robert Israel, Mar 06 2023
MATHEMATICA
Table[If[n == 1, a[1] = 2, j = a[n - 1] + 2; While[a[n] = j; !
AllTrue[Table[a[i] + a[n] + 1, {i, 1, n}], PrimeQ], j += 2]; j]
, {n, 1, 9}] (* Robert Price, Apr 03 2019 *)
PROG
(PARI) isok(va, k, n) = if (isprime(2*k+1), for (i=1, n-1, if (! isprime(va[i]+k+1), return(0))); return(1));
lista(nn) = my(va=vector(nn)); va[1]=2; for (n=2, nn, my(k=va[n-1]+2); while (!isok(va, k, n), k+=2); va[n] = k); va; \\ Michel Marcus, Mar 06 2023
CROSSREFS
Cf. A119751.
Sequence in context: A039660 A333053 A333054 * A111001 A055258 A277649
KEYWORD
nonn,more,hard
AUTHOR
Walter Kehowski, Jun 17 2006
EXTENSIONS
a(13)-a(14) from Donovan Johnson, Mar 23 2008
STATUS
approved

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Last modified April 22 01:34 EDT 2024. Contains 371887 sequences. (Running on oeis4.)