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A344175
Primes of the form 2*3^a+5^b where 3^a+2*5^b is also prime, and a,b >= 1.
1
11, 23, 31, 43, 59, 179, 643, 2083, 13127, 15643, 15679, 42491, 1078507, 3579271, 19331563, 86094067, 6103515643, 8194271927, 783860159531, 15251196923099, 45753585300547, 411782264189423, 477025444560779, 1490116182146884843, 2390683931166760351, 186275633044228814171, 931322574615478517083
OFFSET
1,1
COMMENTS
All terms == 3 (mod 4).
LINKS
EXAMPLE
a(3) = 31 is a term because 31 = 2*3^1+5^2 and 3^1+2*5^2 = 53 are prime.
MAPLE
N:= 10^25: # for terms <= N
R:= NULL:
for a from 1 while 2*3^a < N do
for b from 1 do
x:= 2*3^a+5^b;
if x > N then break fi;
if isprime(x) and isprime(3^a + 2*5^b) then R:= R, x fi
od od:
sort([R]);
CROSSREFS
Sequence in context: A110786 A059642 A090920 * A126330 A090506 A250215
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, May 11 2021
STATUS
approved