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A215895 Primes p with property that there exists a number D such that p-3D, p-2D, p-D, p+D, p+2D, p+3D are all primes. 2
457, 677, 809, 829, 1039, 1249, 1453, 1459, 1511, 1721, 2083, 2879, 3203, 3499, 3527, 3581, 3919, 4129, 4139, 4157, 4273, 4339, 4549, 5519, 5689, 5711, 5843, 6143, 6329, 6359, 6619, 6803, 6949, 7001, 7013, 7103, 7109, 7211, 7393, 7459, 7477, 7481, 7549, 7673, 7723, 7789 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Conjecture: only 130633 primes are not in the sequence: 2, 3, ..., 94532497.
LINKS
Alois P. Heinz and Lei Zhou, Table of n, a(n) for n = 1..10000 (terms n = 1..2000 from Alois P. Heinz)
EXAMPLE
457 is in the sequence because with D=150: 7, 157, 307, 607, 757, 907 are all primes.
MAPLE
a:= proc(n) option remember; local D, p;
p:= `if`(n=1, 1, a(n-1));
do p:= nextprime(p);
for D to iquo(p, 3) do
if nops(select(isprime, {(p-k*D)$k=-3..3}))=7
then return p fi
od
od
end:
seq (a(n), n=1..40); # Alois P. Heinz, Aug 26 2012
MATHEMATICA
a[n_] := a[n] = Module[{D, p}, p = If[n==1, 1, a[n-1]]; While[True, p = NextPrime[p]; For[D = 1, D <= Quotient[p, 3], D++, If[AllTrue[p - Range[-3, 3] D, PrimeQ], Return [p]]]]];
Array[a, 40] (* Jean-François Alcover, Nov 13 2020, after Alois P. Heinz *)
CROSSREFS
Cf. A215642.
Sequence in context: A036271 A061326 A325086 * A142828 A020364 A337847
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Aug 25 2012
STATUS
approved

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Last modified February 26 10:28 EST 2024. Contains 370346 sequences. (Running on oeis4.)