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A228589 Starting from a(1)=1, a(n) is the minimum integer greater than a(n-1) such that a(n)+a(n-1) and a(n)*a(n-1)-1 are both primes. 3
1, 4, 15, 16, 27, 32, 57, 70, 81, 92, 147, 164, 183, 200, 231, 232, 255, 266, 327, 356, 387, 400, 423, 430, 561, 562, 567, 584, 645, 716, 717, 764, 807, 812, 855, 866, 1005, 1006, 1083, 1138, 1203, 1208, 1233, 1298, 1359, 1372, 1395, 1396, 1455, 1498, 1551, 1568 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Terms are alternately odd and even.
LINKS
EXAMPLE
a(5)=27 and 27+28=55, 27+29=56, 27+30=57, 27+31=58 are not prime but 27+32=59 is prime and also 27*32-1=863. Thus a(6)=32.
MAPLE
with(numtheory); P:=proc(q) local a, b, n; a:=1; b:=0; print(a);
for n from 1 to q do while not isprime(a+b) and not isprime (a*b-1) do
b:=b+2; od; print(b); a:=b; b:=b+1; od; print(); end: P(10^4);
CROSSREFS
Sequence in context: A152442 A161769 A135658 * A066862 A228590 A103540
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Aug 27 2013
STATUS
approved

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Last modified March 19 09:40 EDT 2024. Contains 370981 sequences. (Running on oeis4.)