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A361988
a(n) is the least prime == 2*a(n-2) mod a(n-1); a(1) = 2, a(2) = 3.
1
2, 3, 7, 13, 53, 79, 659, 6089, 104831, 955657, 20278459, 103303609, 557074963, 1877832107, 2991982033, 6747646247, 12731610313, 179006226563, 10944843040969, 76971913739909, 98861599821847, 7568563814118343, 492154371117335989, 8381761436622948499, 177001298911316590457, 6919814180414592924821
OFFSET
1,1
COMMENTS
The sequence of least primes == 2*a(n-1) mod a(n-2), starting with a(1) = 2 and a(2) = 3, is 2, 3, 2, 7, 2, 11, 2, 37, 2, 41, 2, 127, 2, 131, ..., the interleaving of 2 and A362005.
LINKS
EXAMPLE
a(4) = 13 because 13 is the first prime == 2*3 (mod 7).
MAPLE
A[1]:= 2: A[2]:= 3:
for i from 3 to 30 do
for k from 2*A[i-2] mod A[i-1] by A[i-1] do
if isprime(k) then A[i]:= k; break fi
od
od:
seq(A[i], i=1..30);
CROSSREFS
Cf. A362005.
Sequence in context: A257393 A273814 A371131 * A085872 A070858 A061067
KEYWORD
nonn
AUTHOR
Robert Israel, Apr 02 2023
STATUS
approved